Add the specified request to the list of received
        PROPAGATEs.

        :param req: the REQUEST to add
        :param sender: the name of the node sending the msg

def add_propagate(self, req: Request, sender: str):
        """
        Add the specified request to the list of received
        PROPAGATEs.

        :param req: the REQUEST to add
        :param sender: the name of the node sending the msg
        """
        data = self.add(req)
        data.propagates[sender] = req