def _duration_string_ms(duration):
    """
    Format a "short" duration string with only minutes and seconds. This is
    intended to fit better in smaller spaces on a graph.
    :returns: a string of the form Xm.
    """
    h, m, s = duration_parts(duration)
    return "{}m{}s".format(m, s)

    Format a "short" duration string with only minutes and seconds. This is
    intended to fit better in smaller spaces on a graph.
    :returns: a string of the form Xm.
    
reports/graphs/feeding_duration.py