Optimize SafeHandleExtensions.Lease()

Implements changes suggested in https://github.com/dotnet/roslyn/pull/43462.

src/TensorFlowNET.Core/Util/SafeHandleExtensions.cs

@@ -15,6 +15,7 @@
 ******************************************************************************/
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 
 namespace Tensorflow.Util
@@ -22,9 +23,14 @@ namespace Tensorflow.Util
     internal static class SafeHandleExtensions
     {
         /// <summary>
-        /// Acquires a lease on a safe handle. This method is intended to be used in the initializer of a <c>using</c>
-        /// statement.
+        /// Acquires a lease on a safe handle. The lease increments the reference count of the <see cref="SafeHandle"/>
+        /// to ensure the handle is not released prior to the lease being released.
         /// </summary>
+        /// <remarks>
+        /// This method is intended to be used in the initializer of a <c>using</c> statement. Failing to release the
+        /// lease will permanently prevent the underlying <see cref="SafeHandle"/> from being released by the garbage
+        /// collector.
+        /// </remarks>
         /// <param name="handle">The <see cref="SafeHandle"/> to lease.</param>
         /// <returns>A <see cref="SafeHandleLease"/>, which must be disposed to release the resource.</returns>
         /// <exception cref="ObjectDisposedException">If the lease could not be acquired.</exception>
@@ -37,8 +43,7 @@ namespace Tensorflow.Util
             try
             {
                 handle.DangerousAddRef(ref success);
-                if (!success)
-                    throw new ObjectDisposedException(handle.GetType().FullName);
+                Debug.Assert(success, $"'{nameof(SafeHandle.DangerousAddRef)}' does not return when '{nameof(success)}' is false.");
 
                 return new SafeHandleLease(handle);
             }