def _gc_dead_sinks(self):
deadsinks = []<EOL>for i in self._sinks:<EOL><INDENT>if i() is None:<EOL><INDENT>deadsinks.append(i)<EOL><DEDENT><DEDENT>for i in deadsinks:<EOL><INDENT>self._sinks.remove(i)<EOL><DEDENT>
Remove any dead weakrefs.