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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 query(self, search, query):
 """ Add query part to ``search``. Override this if you wish to customize the query used. """

        if query:
            if self.fields:
                return search.query('multi_match', fields=self.fields, query=query)
            else:
                return search.query('multi_match', query=query)
        return search