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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 drop_retention_policy(self, name, database=None):
 """Drop an existing retention policy for a database. :param name: the name of the retention policy to drop :type name: str :param database: the database for which the retention policy is dropped. Defaults to current client's database :type database: str """

        query_string = (
            "DROP RETENTION POLICY {0} ON {1}"
        ).format(quote_ident(name), quote_ident(database or self._database))
        self.query(query_string, method="POST")