'Absolute value of a `TimeDelta` object.'

def __abs__(self):

    (jd1, jd2) = (self._time.jd1, self._time.jd2)
    negative = ((jd1 + jd2) < 0)
    new = self.copy()
    new._time.jd1 = np.where(negative, (- jd1), jd1)
    new._time.jd2 = np.where(negative, (- jd2), jd2)
    return new
