code: def doit(
              self, classes=None, recursive=True, indices=None, max_terms=None,
              **kwargs):
          
          return super().doit(
              classes, recursive, indices=indices, max_terms=max_terms, **kwargs)
docs: Write out the indexed sum explicitly
  
          If `classes` is None or :class:`IndexedSum` is in `classes`,
          (partially) write out the indexed sum in to an explicit sum of terms.
          If `recursive` is True, write out each of the new sum's summands by
          calling its :meth:`doit` method.
  
          Args:
              classes (None or list): see :meth:`.Expression.doit`
              recursive (bool): see :meth:`.Expression.doit`
              indices (list): List of :class:`IdxSym` indices for which the sum
                  should be expanded. If `indices` is a subset of the indices
                  over which the sum runs, it will be partially expanded. If not
                  given, expand the sum completely
              max_terms (int): Number of terms after which to truncate the sum.
                  This is particularly useful for infinite sums. If not given,
                  expand all terms of the sum. Cannot be combined with `indices`
              kwargs: keyword arguments for recursive calls to
                  :meth:`doit`. See :meth:`.Expression.doit`