code: def unregister(self, fd):
          
          if self._epfd < 0:
              _err_closed()
          ev = epoll_event()
          try:
              epoll_ctl(self._epfd, EPOLL_CTL_DEL, fd, byref(ev))
          except OSError as exc:
              # Allow fd to be closed, matching Python 3.4
              if exc.errno != EBADF:
                  raise
docs: Unregister a previously registered descriptor
  
          :param fd:
              The descriptor to unregister
          :raises ValueError:
              If :meth:`closed()` is True
          :raises OSError:
              If the underlying ``epoll_ctl(2)`` fails. The error message matches
              those found in the manual page.
  
          .. note::
              For feature parity with Python 3.4, unlike what ``epoll_ctl(2)``
              would do, we are silently ignoring ``EBADF`` which is raised if