The class for a row in this list.

def Row(self):
        """
        The class for a row in this list.
        """
        if not hasattr(self, '_row_class'):
            attrs = {'fields': self.fields, 'list': self, 'opener': self.opener}
            for field in self.fields.values():
                attrs[field.name] = field.descriptor
            self._row_class = type('SharePointListRow', (SharePointListRow,), attrs)
        return self._row_class