'Given a _ConnectionRecord, return it to the :class:`.Pool`.
This method is called when an instrumented DBAPI connection
has its ``close()`` method called.'

def _return_conn(self, record):

    if self._use_threadlocal:
        try:
            del self._threadconns.current
        except AttributeError:
            pass
    self._do_return_conn(record)
