code: def unregister(self, fileobj):
          
          fd = _get_fd(fileobj)
          key = self._fd_map[fd]
          try:
              self._epoll.unregister(fd)
          except OSError:
              pass
          del self._fd_map[fd]
          return key
docs: Remove interest in IO events from the specified fileobj
  
          :param fileobj:
              Any existing file-like object that has a fileno() method and was
              previously registered with :meth:`register()`
          :raises ValueError:
              if `fileobj` is invalid or not supported
          :raises KeyError:
              if the descriptor associated with `fileobj` is not registered.
          :returns:
              A :class:`SelectorKey` associated with the passed arguments