Takes a list of the following form: [(a1, b1), (a2, b2), ...] and
    returns a string a_mean-b_mean, flooring out at 0.

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))