<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def store_magic_envelope_doc(self, payload):
 """Get the Magic Envelope, trying JSON first."""

        try:
            json_payload = json.loads(decode_if_bytes(payload))
        except ValueError:
            # XML payload
            xml = unquote(decode_if_bytes(payload))
            xml = xml.lstrip().encode("utf-8")
            logger.debug("diaspora.protocol.store_magic_envelope_doc: xml payload: %s", xml)
            self.doc = etree.fromstring(xml)
        else:
            logger.debug("diaspora.protocol.store_magic_envelope_doc: json payload: %s", json_payload)
            self.doc = self.get_json_payload_magic_envelope(json_payload)