docs: def display_timestamps_pair_compact(time_m_2):
      """Takes a list of the following form: [(a1, b1), (a2, b2), ...] and
      returns a string a_mean-b_mean, flooring out at 0.
      """
      if len(time_m_2) == 0:
          return '(empty)'
  
      time_m_2 = np.array(time_m_2)
  
      low = time_m_2[:, 0].mean()
      high = time_m_2[:, 1].mean()
  
      low = max(low, 0)
  
      # Not sure if this'll always be true, and not worth crashing over
      if high < 0:
          logger.warn('Harmless warning: upper-bound on clock skew is negative: (%s, %s). Please let Greg know about this.', low, high)
  
      return '{}-{}'.format(display_timestamp(low), display_timestamp(high))