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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 _dispose(self):
 """Dispose of the pool for this instance, closing all connections."""

        self.close()
        # _DBProxy.dispose doesn't actually call dispose on the pool
        conn_params = self.get_connection_params()
        key = db_pool._serialize(**conn_params)
        try:
            pool = db_pool.pools[key]
        except KeyError:
            pass
        else:
            pool.dispose()
            del db_pool.pools[key]