Update model_utils.py (#134)

I ran into an issue where save_layer in model_utils.py is giving me an error that: AttributeError: 'Dense' object has no attribute 'output_shape'

I found that layer.output.shape works, but isn't always a tuple, which runs afoul of the JSON encoder. So I added check for that too.

I modified the code and it seems to work on Macos, Linux, Windows. I've included my debugging print statements so you can see what I was looking at.

python/model_utils.py

@@ -72,10 +72,17 @@ def get_layer_activation(layer):
 
 
     def save_layer(layer):
+        try:
+            outshape = layer.output_shape # this is the original code, but sometimes doesn't work
+        except:
+            outshape = layer.output.shape # if not, use this and make sure it's a tuple so it can be JSON encoded
+            if type(outshape) != tuple:  
+                outshape = tuple(outshape.as_list())
+
         layer_dict = {
             "type"       : get_layer_type(layer),
             "activation" : get_layer_activation(layer),
-            "shape"      : layer.output_shape,
+            "shape"      : outshape, # modified to use the outshape above
         }
 
         if layer_dict["type"] == "conv1d":