Removed a mistake in code

SystemExtensions/Collections/AVLTree.cs

@@ -14,7 +14,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type.</typeparam>
     [Serializable]
-    public class AVLTree<T> : ICollection<T> where T : IComparable<T>
+    public sealed class AVLTree<T> : ICollection<T> where T : IComparable<T>
     {
         #region Fields
         [Serializable]

SystemExtensions/Collections/BinaryHeap.cs

@@ -12,7 +12,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type.</typeparam>
     [Serializable]
-    public class BinaryHeap<T> : IEnumerable<T> where T : IComparable<T>
+    public sealed class BinaryHeap<T> : IEnumerable<T> where T : IComparable<T>
     {
         #region Fields
         T[] items;

SystemExtensions/Collections/FibonacciHeap.cs

@@ -12,7 +12,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type</typeparam>
     [Serializable]
-    public class FibonacciHeap<T> : IEnumerable<T> where T : IComparable<T>
+    public sealed class FibonacciHeap<T> : IEnumerable<T> where T : IComparable<T>
     {
         #region Fields
         private FibonacciNode<T> root;
@@ -462,7 +462,7 @@ namespace SystemExtensions.Collections
         #endregion
     }
     [Serializable]
-    internal class FibonacciNode<T>
+    internal sealed class FibonacciNode<T>
     {
         #region Fields
         private FibonacciNode<T> previous;

SystemExtensions/Collections/PriorityQueue.cs

@@ -13,7 +13,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type.</typeparam>
     [Serializable]
-    public class PriorityQueue<T> : IQueue<T> where T : IComparable<T>
+    public sealed class PriorityQueue<T> : IQueue<T> where T : IComparable<T>
     {
         #region Fields
         private BinaryHeap<T> binaryHeap;

SystemExtensions/Collections/SkipList.cs

@@ -12,7 +12,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type.</typeparam>
     [Serializable]
-    public class SkipList<T> : ICollection<T> where T : IComparable<T>
+    public sealed class SkipList<T> : ICollection<T> where T : IComparable<T>
     {
         #region Fields
         [Serializable]

SystemExtensions/Collections/Treap.cs

@@ -12,7 +12,7 @@ namespace SystemExtensions.Collections
     /// </summary>
     /// <typeparam name="T">Provided type.</typeparam>
     [Serializable]
-    public class Treap<T> : ICollection<T> where T : IComparable<T>
+    public sealed class Treap<T> : ICollection<T> where T : IComparable<T>
     {
         #region Fields
         [Serializable]