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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 import_to_gluon(model_file, ctx):
 """ Imports the ONNX model files, passed as a parameter, into Gluon SymbolBlock object. Parameters model_file : str ONNX model file name ctx : Context or list of Context Loads the model into one or many context(s). Returns ------- sym_block : :class:`~mxnet.gluon.SymbolBlock` A SymbolBlock object representing the given model file. Notes ----- This method is available when you ``import mxnet.contrib.onnx`` """

    graph = GraphProto()
    try:
        import onnx
    except ImportError:
        raise ImportError("Onnx and protobuf need to be installed. Instructions to"
                          + " install - https://github.com/onnx/onnx#installation")
    model_proto = onnx.load_model(model_file)
    net = graph.graph_to_gluon(model_proto.graph, ctx)
    return net