def METHOD_NAME(self):
    model = test_models_keras.concat_functional()
    for layer in model.layers:
        assert layer.inbound_nodes
    connected_graph = ConnectedGraph(model)
    for layer in connected_graph._model.layers:
        assert layer.inbound_nodes
    assert len(connected_graph.get_all_ops().keys()) == 6
    concat_op = connected_graph.get_all_ops()['Concat_3']
    assert len(concat_op.inputs) == 3