diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/byte.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/byte.go
new file mode 100644
index 0000000..766f450
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/byte.go
@@ -0,0 +1,203 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+package sets
+
+import (
+	"reflect"
+	"sort"
+)
+
+// sets.Byte is a set of bytes, implemented via map[byte]struct{} for minimal memory consumption.
+type Byte map[byte]Empty
+
+// NewByte creates a Byte from a list of values.
+func NewByte(items ...byte) Byte {
+	ss := Byte{}
+	ss.Insert(items...)
+	return ss
+}
+
+// ByteKeySet creates a Byte from a keys of a map[byte](? extends interface{}).
+// If the value passed in is not actually a map, this will panic.
+func ByteKeySet(theMap interface{}) Byte {
+	v := reflect.ValueOf(theMap)
+	ret := Byte{}
+
+	for _, keyValue := range v.MapKeys() {
+		ret.Insert(keyValue.Interface().(byte))
+	}
+	return ret
+}
+
+// Insert adds items to the set.
+func (s Byte) Insert(items ...byte) {
+	for _, item := range items {
+		s[item] = Empty{}
+	}
+}
+
+// Delete removes all items from the set.
+func (s Byte) Delete(items ...byte) {
+	for _, item := range items {
+		delete(s, item)
+	}
+}
+
+// Has returns true if and only if item is contained in the set.
+func (s Byte) Has(item byte) bool {
+	_, contained := s[item]
+	return contained
+}
+
+// HasAll returns true if and only if all items are contained in the set.
+func (s Byte) HasAll(items ...byte) bool {
+	for _, item := range items {
+		if !s.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// HasAny returns true if any items are contained in the set.
+func (s Byte) HasAny(items ...byte) bool {
+	for _, item := range items {
+		if s.Has(item) {
+			return true
+		}
+	}
+	return false
+}
+
+// Difference returns a set of objects that are not in s2
+// For example:
+// s1 = {a1, a2, a3}
+// s2 = {a1, a2, a4, a5}
+// s1.Difference(s2) = {a3}
+// s2.Difference(s1) = {a4, a5}
+func (s Byte) Difference(s2 Byte) Byte {
+	result := NewByte()
+	for key := range s {
+		if !s2.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// Union returns a new set which includes items in either s1 or s2.
+// For example:
+// s1 = {a1, a2}
+// s2 = {a3, a4}
+// s1.Union(s2) = {a1, a2, a3, a4}
+// s2.Union(s1) = {a1, a2, a3, a4}
+func (s1 Byte) Union(s2 Byte) Byte {
+	result := NewByte()
+	for key := range s1 {
+		result.Insert(key)
+	}
+	for key := range s2 {
+		result.Insert(key)
+	}
+	return result
+}
+
+// Intersection returns a new set which includes the item in BOTH s1 and s2
+// For example:
+// s1 = {a1, a2}
+// s2 = {a2, a3}
+// s1.Intersection(s2) = {a2}
+func (s1 Byte) Intersection(s2 Byte) Byte {
+	var walk, other Byte
+	result := NewByte()
+	if s1.Len() < s2.Len() {
+		walk = s1
+		other = s2
+	} else {
+		walk = s2
+		other = s1
+	}
+	for key := range walk {
+		if other.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// IsSuperset returns true if and only if s1 is a superset of s2.
+func (s1 Byte) IsSuperset(s2 Byte) bool {
+	for item := range s2 {
+		if !s1.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equal returns true if and only if s1 is equal (as a set) to s2.
+// Two sets are equal if their membership is identical.
+// (In practice, this means same elements, order doesn't matter)
+func (s1 Byte) Equal(s2 Byte) bool {
+	return len(s1) == len(s2) && s1.IsSuperset(s2)
+}
+
+type sortableSliceOfByte []byte
+
+func (s sortableSliceOfByte) Len() int           { return len(s) }
+func (s sortableSliceOfByte) Less(i, j int) bool { return lessByte(s[i], s[j]) }
+func (s sortableSliceOfByte) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// List returns the contents as a sorted byte slice.
+func (s Byte) List() []byte {
+	res := make(sortableSliceOfByte, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	sort.Sort(res)
+	return []byte(res)
+}
+
+// UnsortedList returns the slice with contents in random order.
+func (s Byte) UnsortedList() []byte {
+	res := make([]byte, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	return res
+}
+
+// Returns a single element from the set.
+func (s Byte) PopAny() (byte, bool) {
+	for key := range s {
+		s.Delete(key)
+		return key, true
+	}
+	var zeroValue byte
+	return zeroValue, false
+}
+
+// Len returns the size of the set.
+func (s Byte) Len() int {
+	return len(s)
+}
+
+func lessByte(lhs, rhs byte) bool {
+	return lhs < rhs
+}
diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/doc.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/doc.go
new file mode 100644
index 0000000..b152a0b
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/doc.go
@@ -0,0 +1,20 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+// Package sets has auto-generated set types.
+package sets
diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/empty.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/empty.go
new file mode 100644
index 0000000..e11e622
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/empty.go
@@ -0,0 +1,23 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+package sets
+
+// Empty is public since it is used by some internal API objects for conversions between external
+// string arrays and internal sets, and conversion logic requires public types today.
+type Empty struct{}
diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int.go
new file mode 100644
index 0000000..a0a513c
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int.go
@@ -0,0 +1,203 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+package sets
+
+import (
+	"reflect"
+	"sort"
+)
+
+// sets.Int is a set of ints, implemented via map[int]struct{} for minimal memory consumption.
+type Int map[int]Empty
+
+// NewInt creates a Int from a list of values.
+func NewInt(items ...int) Int {
+	ss := Int{}
+	ss.Insert(items...)
+	return ss
+}
+
+// IntKeySet creates a Int from a keys of a map[int](? extends interface{}).
+// If the value passed in is not actually a map, this will panic.
+func IntKeySet(theMap interface{}) Int {
+	v := reflect.ValueOf(theMap)
+	ret := Int{}
+
+	for _, keyValue := range v.MapKeys() {
+		ret.Insert(keyValue.Interface().(int))
+	}
+	return ret
+}
+
+// Insert adds items to the set.
+func (s Int) Insert(items ...int) {
+	for _, item := range items {
+		s[item] = Empty{}
+	}
+}
+
+// Delete removes all items from the set.
+func (s Int) Delete(items ...int) {
+	for _, item := range items {
+		delete(s, item)
+	}
+}
+
+// Has returns true if and only if item is contained in the set.
+func (s Int) Has(item int) bool {
+	_, contained := s[item]
+	return contained
+}
+
+// HasAll returns true if and only if all items are contained in the set.
+func (s Int) HasAll(items ...int) bool {
+	for _, item := range items {
+		if !s.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// HasAny returns true if any items are contained in the set.
+func (s Int) HasAny(items ...int) bool {
+	for _, item := range items {
+		if s.Has(item) {
+			return true
+		}
+	}
+	return false
+}
+
+// Difference returns a set of objects that are not in s2
+// For example:
+// s1 = {a1, a2, a3}
+// s2 = {a1, a2, a4, a5}
+// s1.Difference(s2) = {a3}
+// s2.Difference(s1) = {a4, a5}
+func (s Int) Difference(s2 Int) Int {
+	result := NewInt()
+	for key := range s {
+		if !s2.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// Union returns a new set which includes items in either s1 or s2.
+// For example:
+// s1 = {a1, a2}
+// s2 = {a3, a4}
+// s1.Union(s2) = {a1, a2, a3, a4}
+// s2.Union(s1) = {a1, a2, a3, a4}
+func (s1 Int) Union(s2 Int) Int {
+	result := NewInt()
+	for key := range s1 {
+		result.Insert(key)
+	}
+	for key := range s2 {
+		result.Insert(key)
+	}
+	return result
+}
+
+// Intersection returns a new set which includes the item in BOTH s1 and s2
+// For example:
+// s1 = {a1, a2}
+// s2 = {a2, a3}
+// s1.Intersection(s2) = {a2}
+func (s1 Int) Intersection(s2 Int) Int {
+	var walk, other Int
+	result := NewInt()
+	if s1.Len() < s2.Len() {
+		walk = s1
+		other = s2
+	} else {
+		walk = s2
+		other = s1
+	}
+	for key := range walk {
+		if other.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// IsSuperset returns true if and only if s1 is a superset of s2.
+func (s1 Int) IsSuperset(s2 Int) bool {
+	for item := range s2 {
+		if !s1.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equal returns true if and only if s1 is equal (as a set) to s2.
+// Two sets are equal if their membership is identical.
+// (In practice, this means same elements, order doesn't matter)
+func (s1 Int) Equal(s2 Int) bool {
+	return len(s1) == len(s2) && s1.IsSuperset(s2)
+}
+
+type sortableSliceOfInt []int
+
+func (s sortableSliceOfInt) Len() int           { return len(s) }
+func (s sortableSliceOfInt) Less(i, j int) bool { return lessInt(s[i], s[j]) }
+func (s sortableSliceOfInt) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// List returns the contents as a sorted int slice.
+func (s Int) List() []int {
+	res := make(sortableSliceOfInt, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	sort.Sort(res)
+	return []int(res)
+}
+
+// UnsortedList returns the slice with contents in random order.
+func (s Int) UnsortedList() []int {
+	res := make([]int, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	return res
+}
+
+// Returns a single element from the set.
+func (s Int) PopAny() (int, bool) {
+	for key := range s {
+		s.Delete(key)
+		return key, true
+	}
+	var zeroValue int
+	return zeroValue, false
+}
+
+// Len returns the size of the set.
+func (s Int) Len() int {
+	return len(s)
+}
+
+func lessInt(lhs, rhs int) bool {
+	return lhs < rhs
+}
diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int64.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int64.go
new file mode 100644
index 0000000..9ca9af0
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/int64.go
@@ -0,0 +1,203 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+package sets
+
+import (
+	"reflect"
+	"sort"
+)
+
+// sets.Int64 is a set of int64s, implemented via map[int64]struct{} for minimal memory consumption.
+type Int64 map[int64]Empty
+
+// NewInt64 creates a Int64 from a list of values.
+func NewInt64(items ...int64) Int64 {
+	ss := Int64{}
+	ss.Insert(items...)
+	return ss
+}
+
+// Int64KeySet creates a Int64 from a keys of a map[int64](? extends interface{}).
+// If the value passed in is not actually a map, this will panic.
+func Int64KeySet(theMap interface{}) Int64 {
+	v := reflect.ValueOf(theMap)
+	ret := Int64{}
+
+	for _, keyValue := range v.MapKeys() {
+		ret.Insert(keyValue.Interface().(int64))
+	}
+	return ret
+}
+
+// Insert adds items to the set.
+func (s Int64) Insert(items ...int64) {
+	for _, item := range items {
+		s[item] = Empty{}
+	}
+}
+
+// Delete removes all items from the set.
+func (s Int64) Delete(items ...int64) {
+	for _, item := range items {
+		delete(s, item)
+	}
+}
+
+// Has returns true if and only if item is contained in the set.
+func (s Int64) Has(item int64) bool {
+	_, contained := s[item]
+	return contained
+}
+
+// HasAll returns true if and only if all items are contained in the set.
+func (s Int64) HasAll(items ...int64) bool {
+	for _, item := range items {
+		if !s.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// HasAny returns true if any items are contained in the set.
+func (s Int64) HasAny(items ...int64) bool {
+	for _, item := range items {
+		if s.Has(item) {
+			return true
+		}
+	}
+	return false
+}
+
+// Difference returns a set of objects that are not in s2
+// For example:
+// s1 = {a1, a2, a3}
+// s2 = {a1, a2, a4, a5}
+// s1.Difference(s2) = {a3}
+// s2.Difference(s1) = {a4, a5}
+func (s Int64) Difference(s2 Int64) Int64 {
+	result := NewInt64()
+	for key := range s {
+		if !s2.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// Union returns a new set which includes items in either s1 or s2.
+// For example:
+// s1 = {a1, a2}
+// s2 = {a3, a4}
+// s1.Union(s2) = {a1, a2, a3, a4}
+// s2.Union(s1) = {a1, a2, a3, a4}
+func (s1 Int64) Union(s2 Int64) Int64 {
+	result := NewInt64()
+	for key := range s1 {
+		result.Insert(key)
+	}
+	for key := range s2 {
+		result.Insert(key)
+	}
+	return result
+}
+
+// Intersection returns a new set which includes the item in BOTH s1 and s2
+// For example:
+// s1 = {a1, a2}
+// s2 = {a2, a3}
+// s1.Intersection(s2) = {a2}
+func (s1 Int64) Intersection(s2 Int64) Int64 {
+	var walk, other Int64
+	result := NewInt64()
+	if s1.Len() < s2.Len() {
+		walk = s1
+		other = s2
+	} else {
+		walk = s2
+		other = s1
+	}
+	for key := range walk {
+		if other.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// IsSuperset returns true if and only if s1 is a superset of s2.
+func (s1 Int64) IsSuperset(s2 Int64) bool {
+	for item := range s2 {
+		if !s1.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equal returns true if and only if s1 is equal (as a set) to s2.
+// Two sets are equal if their membership is identical.
+// (In practice, this means same elements, order doesn't matter)
+func (s1 Int64) Equal(s2 Int64) bool {
+	return len(s1) == len(s2) && s1.IsSuperset(s2)
+}
+
+type sortableSliceOfInt64 []int64
+
+func (s sortableSliceOfInt64) Len() int           { return len(s) }
+func (s sortableSliceOfInt64) Less(i, j int) bool { return lessInt64(s[i], s[j]) }
+func (s sortableSliceOfInt64) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// List returns the contents as a sorted int64 slice.
+func (s Int64) List() []int64 {
+	res := make(sortableSliceOfInt64, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	sort.Sort(res)
+	return []int64(res)
+}
+
+// UnsortedList returns the slice with contents in random order.
+func (s Int64) UnsortedList() []int64 {
+	res := make([]int64, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	return res
+}
+
+// Returns a single element from the set.
+func (s Int64) PopAny() (int64, bool) {
+	for key := range s {
+		s.Delete(key)
+		return key, true
+	}
+	var zeroValue int64
+	return zeroValue, false
+}
+
+// Len returns the size of the set.
+func (s Int64) Len() int {
+	return len(s)
+}
+
+func lessInt64(lhs, rhs int64) bool {
+	return lhs < rhs
+}
diff --git a/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/string.go b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/string.go
new file mode 100644
index 0000000..ba00ad7
--- /dev/null
+++ b/metrics-server/vendor/k8s.io/gengo/examples/set-gen/sets/string.go
@@ -0,0 +1,203 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Code generated by set-gen. DO NOT EDIT.
+
+package sets
+
+import (
+	"reflect"
+	"sort"
+)
+
+// sets.String is a set of strings, implemented via map[string]struct{} for minimal memory consumption.
+type String map[string]Empty
+
+// NewString creates a String from a list of values.
+func NewString(items ...string) String {
+	ss := String{}
+	ss.Insert(items...)
+	return ss
+}
+
+// StringKeySet creates a String from a keys of a map[string](? extends interface{}).
+// If the value passed in is not actually a map, this will panic.
+func StringKeySet(theMap interface{}) String {
+	v := reflect.ValueOf(theMap)
+	ret := String{}
+
+	for _, keyValue := range v.MapKeys() {
+		ret.Insert(keyValue.Interface().(string))
+	}
+	return ret
+}
+
+// Insert adds items to the set.
+func (s String) Insert(items ...string) {
+	for _, item := range items {
+		s[item] = Empty{}
+	}
+}
+
+// Delete removes all items from the set.
+func (s String) Delete(items ...string) {
+	for _, item := range items {
+		delete(s, item)
+	}
+}
+
+// Has returns true if and only if item is contained in the set.
+func (s String) Has(item string) bool {
+	_, contained := s[item]
+	return contained
+}
+
+// HasAll returns true if and only if all items are contained in the set.
+func (s String) HasAll(items ...string) bool {
+	for _, item := range items {
+		if !s.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// HasAny returns true if any items are contained in the set.
+func (s String) HasAny(items ...string) bool {
+	for _, item := range items {
+		if s.Has(item) {
+			return true
+		}
+	}
+	return false
+}
+
+// Difference returns a set of objects that are not in s2
+// For example:
+// s1 = {a1, a2, a3}
+// s2 = {a1, a2, a4, a5}
+// s1.Difference(s2) = {a3}
+// s2.Difference(s1) = {a4, a5}
+func (s String) Difference(s2 String) String {
+	result := NewString()
+	for key := range s {
+		if !s2.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// Union returns a new set which includes items in either s1 or s2.
+// For example:
+// s1 = {a1, a2}
+// s2 = {a3, a4}
+// s1.Union(s2) = {a1, a2, a3, a4}
+// s2.Union(s1) = {a1, a2, a3, a4}
+func (s1 String) Union(s2 String) String {
+	result := NewString()
+	for key := range s1 {
+		result.Insert(key)
+	}
+	for key := range s2 {
+		result.Insert(key)
+	}
+	return result
+}
+
+// Intersection returns a new set which includes the item in BOTH s1 and s2
+// For example:
+// s1 = {a1, a2}
+// s2 = {a2, a3}
+// s1.Intersection(s2) = {a2}
+func (s1 String) Intersection(s2 String) String {
+	var walk, other String
+	result := NewString()
+	if s1.Len() < s2.Len() {
+		walk = s1
+		other = s2
+	} else {
+		walk = s2
+		other = s1
+	}
+	for key := range walk {
+		if other.Has(key) {
+			result.Insert(key)
+		}
+	}
+	return result
+}
+
+// IsSuperset returns true if and only if s1 is a superset of s2.
+func (s1 String) IsSuperset(s2 String) bool {
+	for item := range s2 {
+		if !s1.Has(item) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equal returns true if and only if s1 is equal (as a set) to s2.
+// Two sets are equal if their membership is identical.
+// (In practice, this means same elements, order doesn't matter)
+func (s1 String) Equal(s2 String) bool {
+	return len(s1) == len(s2) && s1.IsSuperset(s2)
+}
+
+type sortableSliceOfString []string
+
+func (s sortableSliceOfString) Len() int           { return len(s) }
+func (s sortableSliceOfString) Less(i, j int) bool { return lessString(s[i], s[j]) }
+func (s sortableSliceOfString) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// List returns the contents as a sorted string slice.
+func (s String) List() []string {
+	res := make(sortableSliceOfString, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	sort.Sort(res)
+	return []string(res)
+}
+
+// UnsortedList returns the slice with contents in random order.
+func (s String) UnsortedList() []string {
+	res := make([]string, 0, len(s))
+	for key := range s {
+		res = append(res, key)
+	}
+	return res
+}
+
+// Returns a single element from the set.
+func (s String) PopAny() (string, bool) {
+	for key := range s {
+		s.Delete(key)
+		return key, true
+	}
+	var zeroValue string
+	return zeroValue, false
+}
+
+// Len returns the size of the set.
+func (s String) Len() int {
+	return len(s)
+}
+
+func lessString(lhs, rhs string) bool {
+	return lhs < rhs
+}