def get_definition(self):
        '''Returns definition'''
        definition = parsers.get_definition(self.__chebi_id)

        if definition is None:
            definition = parsers.get_definition(self.get_parent_id())

        if definition is None:
            for parent_or_child_id in self.__get_all_ids():
                definition = parsers.get_definition(parent_or_child_id)

                if definition is not None:
                    break

        return definition
Returns definition