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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 write_external_data_tensors(model, filepath):
 # type: (ModelProto, Text) -> ModelProto """ Write external data of all tensors to files on disk. Note: This function also strips basepath information from all tensors' external_data fields. @params model: Model object which is the source of tensors to serialize. filepath: System path to the directory which should be treated as base path for external data. @return The modified model object. """

    for tensor in _get_all_tensors(model):
        if uses_external_data(tensor):
            save_external_data(tensor, filepath)
            tensor.ClearField(str('raw_data'))

    return model