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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):
 """Parse query string using given grammar. :returns: AST that represents the query in the given grammar. """

        tree = pypeg2.parse(self._query, parser(), whitespace="")
        for walker in query_walkers():
            tree = tree.accept(walker)
        return tree