def get_weekend_days(self):
if self.WEEKEND_DAYS:<EOL><INDENT>return self.WEEKEND_DAYS<EOL><DEDENT>else:<EOL><INDENT>raise NotImplementedError("<STR_LIT>"<EOL>"<STR_LIT>"<EOL>"<STR_LIT>")<EOL><DEDENT>
Return a list (or a tuple) of weekdays that are *not* working days.

        e.g: return (SAT, SUN,)