def sub_working_days(self, day, delta,<EOL>extra_working_days=None, extra_holidays=None,<EOL>keep_datetime=False):
delta = abs(delta)<EOL>return self.add_working_days(<EOL>day, -delta,<EOL>extra_working_days, extra_holidays, keep_datetime=keep_datetime)<EOL>
Substract `delta` working days to the date.

This method is a shortcut / helper. Users may want to use either::

    cal.add_working_days(my_date, -7)
    cal.sub_working_days(my_date, 7)

The other parameters are to be used exactly as in the
``add_working_days`` method.

A negative ``delta`` argument will be converted into its absolute
value. Hence, the two following calls are equivalent::

    cal.sub_working_days(my_date, -7)
    cal.sub_working_days(my_date, 7)

As in ``add_working_days()`` you can set the parameter
``keep_datetime`` to ``True`` to make sure that if your ``day``
argument is a ``datetime``, the returned date will also be a
``datetime`` object.