def METHOD_NAME(a, b):
    '''Add two progress indicators, assuming that each represents items done:
    (a / b) + (c / d) = (a + c) / (b + d).
    If either is None, returns the other.
    '''
    if a is None:
        return b
    if b is None:
        return a
    # get numerators + denominators
    (n, d) = a.frac()
    (n2, d2) = b.frac()
    return Progress(n + n2, d + d2)