code: def _split_identifier(self, identifier):
          
          try:
              name, subscript = identifier.split("_", 1)
          except (TypeError, ValueError, AttributeError):
              name = identifier
              subscript = ''
          return self._render_str(name), self._render_str(subscript)
docs: Split the given identifier at the first underscore into (rendered)
          name and subscript. Both `name` and `subscript` are rendered as
          strings