<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _process_method_frame(self, channel, payload):
 """ Process Method frames """

        method_sig = unpack('>HH', payload[:4])
        args = AMQPReader(payload[4:])

        if method_sig in _CONTENT_METHODS:
            #
            # Save what we've got so far and wait for the content-header
            #
            self.partial_messages[channel] = _PartialMessage(method_sig, args)
            self.expected_types[channel] = 2
        else:
            self.queue.put((channel, method_sig, args, None))