<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _subtotals(self):
 """Composed tuple storing actual sequence of _Subtotal objects."""

        return tuple(
            _Subtotal(subtotal_dict, self.valid_elements)
            for subtotal_dict in self._iter_valid_subtotal_dicts()
        )