def METHOD_NAME(self, conn: TcpServerConnection) -> None:
    """Retained previously acquired connection in the pool for reusability."""
    assert not conn.closed
    logger.debug(
        'Retaining connection#{2} to upstream {0}:{1}'.format(
            conn.addr[0], conn.addr[1], id(conn),
        ),
    )
    # Reset for reusability
    conn.reset()