def _key_from_fd(self, fd):
        """Return the key associated to a given file descriptor.

        Parameters:
        fd -- file descriptor

        Returns:
        corresponding key, or None if not found
        """
        try:
            return self._fd_to_key[fd]
        except KeyError:
            return None
Return the key associated to a given file descriptor.

        Parameters:
        fd -- file descriptor

        Returns:
        corresponding key, or None if not found
        
kafka/vendor/selectors34.py