Allow ComputeOutputShape to override in subclass #660.

src/TensorFlowNET.Keras/Engine/Layer.Layers.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 
 namespace Tensorflow.Keras.Engine
 {
@@ -11,5 +12,8 @@ namespace Tensorflow.Keras.Engine
         {
             _layers.AddRange(layers);
         }
+
+        public virtual TensorShape ComputeOutputShape(TensorShape input_shape)
+            => throw new NotImplementedException("");
     }
 }

src/TensorFlowNET.Keras/Layers/Reshaping/Reshape.cs

@@ -26,11 +26,11 @@ namespace Tensorflow.Keras.Layers
 
             var result = array_ops.reshape(inputs, shape.ToArray());
             if (!tf.Context.executing_eagerly())
-                result.set_shape(compute_output_shape(inputs.shape));
+                result.set_shape(ComputeOutputShape(inputs.shape));
             return result;
         }
 
-        TensorShape compute_output_shape(TensorShape input_shape)
+        public override TensorShape ComputeOutputShape(TensorShape input_shape)
         {
             if (input_shape.dims[0] == -1)
             {