docs: def add(self, count, timestamp=None):
          """Add a value at the specified time to the series.
  
          :param count: The number of work items ready at the specified
              time.
          :param timestamp: The timestamp to add. Defaults to None,
              meaning current time. It should be strictly greater (newer)
              than the last added timestamp.
          """
          if timestamp is None:
              timestamp = time.time()
          if self.last_data >= timestamp:
              raise ValueError("Time {} >= {} in load average calculation".format(self.last_data, timestamp))
          self.last_data = timestamp
  
          for meta in self.intervals.values():
              meta.push(count, timestamp)