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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 _module_to_generators(pb_module):
    '''
    Convert a protobuf module to a dict of generators.

    This is typically used with modules that contain multiple type definitions.
    '''
    if not pb_module:
        return None
    message_types = pb_module.DESCRIPTOR.message_types_by_name
    return {k: ProtobufGenerator(v) for k, v in message_types.items()}