def set_stream(self,stream):
_unused = stream<EOL>if self.joined and self.handler:<EOL><INDENT>self.handler.user_left(self.me,None)<EOL><DEDENT>self.joined=False<EOL>
Called when current stream changes.

Mark the room not joined and inform `self.handler` that it was left.

:Parameters:
    - `stream`: the new stream.
:Types:
    - `stream`: `pyxmpp.stream.Stream`