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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 get_entity_mm():
 """ Builds and returns a meta-model for Entity language. """

    type_builtins = {
            'integer': SimpleType(None, 'integer'),
            'string': SimpleType(None, 'string')
    }
    entity_mm = metamodel_from_file(join(this_folder, 'entity.tx'),
                                    classes=[SimpleType],
                                    builtins=type_builtins)

    return entity_mm