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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def load_spec(filename):
 """ Load a protobuf model specification from file Parameters filename: str Location on disk (a valid filepath) from which the file is loaded as a protobuf spec. Returns ------- model_spec: Model_pb Protobuf representation of the model Examples -------- .. sourcecode:: python See Also -------- save_spec """

    from ..proto import Model_pb2
    spec = Model_pb2.Model()

    with open(filename, 'rb') as f:
        contents = f.read()
        spec.ParseFromString(contents)
        return spec