Fix ParseSlices for Tensor overload.

src/TensorFlowNET.Core/Tensors/tensor_util.cs

@@ -680,7 +680,7 @@ would not be rank 1.", tensor.op.get_attr("axis")));
             var end = new List<Tensor>();
             var strides = new List<Tensor>();
 
-            // var index = 0;
+            var index = 0;
             var (new_axis_mask, shrink_axis_mask) = (0, 0);
             var (begin_mask, end_mask) = (0, 0);
             var ellipsis_mask = 0;
@@ -692,7 +692,7 @@ would not be rank 1.", tensor.op.get_attr("axis")));
             else
                 end.Add(stop);
 
-            // shrink_axis_mask |= (1 << index);
+            shrink_axis_mask |= (1 << index);
 
             if (step == null)
                 strides.Add(tf.constant(1, dtype: start.dtype));