code: def add_days(self, *days):
          
          for day in list(days):
              self.days.append(day)
docs: Add one or several days to the program.
      
          Parameters
          ----------
          *days
              Unpacked tuple containing
              :py:class:`streprogen.Day` instances.
      
      
          Examples
          -------
          >>> program = Program('My training program')
          >>> day1, day2 = Day(), Day()
          >>> program.add_days(day1, day2)