handle an incoming mavlink packet

def mavlink_packet(self, msg):
        '''handle an incoming mavlink packet'''

        # check for any closed graphs
        for i in range(len(self.graphs) - 1, -1, -1):
            if not self.graphs[i].is_alive():
                self.graphs[i].close()
                self.graphs.pop(i)

        # add data to the rest
        for g in self.graphs:
            g.add_mavlink_packet(msg)