Loads a serialized computing graph as a GraphInference object which can be used to execute the computing graph.
The `GraphInference.run()` accepts a list `inp_args` or a dict `inp_dict` {input_name: input_value} as input and returns a dict {output_name: output_value}.
:param file: could be file object or filename.
:param outputs: only compile the subgraph with outputs as its endpoints.