<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def businesstime_hours(self, d1, d2):
 """ Returns a datetime.timedelta of business hours between d1 and d2, based on the length of the businessday """

        open_hours = self.open_hours.seconds / 3600
        btd = self.businesstimedelta(d1, d2)
        btd_hours = btd.seconds / 3600
        return datetime.timedelta(hours=(btd.days * open_hours + btd_hours))