log the time of some heavy callbacks

def log(self):

        """ log the time of some heavy callbacks """
        if self.tot < 3:
            return
        msgs = []
        for name, t in self.times:
            if t / self.tot > 0.3 and t > 1:
                msgs.append(name + ": " + humanize_time_delta(t))
        logger.info(
            "Callbacks took {:.3f} sec in total. {}".format(
                self.tot, '; '.join(msgs)))