@synchronized(lock)<EOL><INDENT>def has_frames(self, destination):<DEDENT>
return self.size(destination) > <NUM_LIT:0><EOL>
Whether specified destination has any frames.

Default implementation uses L{QueueStore.size} to determine if there
are any frames in queue.  Subclasses may choose to optimize this.

@param destination: The queue destination (e.g. /queue/foo)
@type destination: C{str}

@return: The number of frames in specified queue.
@rtype: C{int}