Added continue statement to as that is what is in the original python file and got rid off cast error

src/TensorFlowNET.Core/Framework/meta_graph.py.cs

@@ -134,7 +134,7 @@ namespace Tensorflow
                                         }
                                         break;
                                     default:
-                                        throw new NotImplementedException("import_scoped_meta_graph_with_return_elements");
+                                        continue;
                                 }
                             }
                         }

src/TensorFlowNET.Core/Train/Optimizer.cs

@@ -199,8 +199,8 @@ namespace Tensorflow
 
                 if (!tf.context.executing_eagerly())
                 {
-                    var train_op = ops.get_collection_ref(ops.GraphKeys.TRAIN_OP) as List<object>;
-                    if (!train_op.Contains(apply_updates))
+                    var train_op = ops.get_collection_ref(ops.GraphKeys.TRAIN_OP) as List<ITensorOrOperation>;
+                    if (train_op != null && train_op.Contains(apply_updates))
                         train_op.Add(apply_updates);
                 }