'Get the duration value between the 2 given dates.'

def _get_duration(self, start, stop):

    if (start and stop):
        diff = (fields.Datetime.from_string(stop) - fields.Datetime.from_string(start))
        if diff:
            duration = ((float(diff.days) * 24) + (float(diff.seconds) / 3600))
            return round(duration, 2)
        return 0.0
