<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def receive( self, request: RequestType, user: UserType = None, sender_key_fetcher: Callable[[str], str] = None, skip_author_verification: bool = False) -> Tuple[str, str]: """Receive a payload. For testing purposes, `skip_author_verification` can be passed. Authorship will not be verified."""

        self.user = user
        self.get_contact_key = sender_key_fetcher
        self.store_magic_envelope_doc(request.body)
        # Open payload and get actual message
        self.content = self.get_message_content()
        # Get sender handle
        self.sender_handle = self.get_sender()
        # Verify the message is from who it claims to be
        if not skip_author_verification:
            self.verify_signature()
        return self.sender_handle, self.content