code: def row_sparse_data(self, row_id):
          
          if self._stype != 'row_sparse':
              raise RuntimeError("Cannot return a copy of Parameter %s via row_sparse_data() " \
                                 "because its storage type is %s. Please use data() instead." \
                                 %(self.name, self._stype))
          return self._get_row_sparse(self._data, row_id.context, row_id)
docs: Returns a copy of the 'row_sparse' parameter on the same context as row_id's.
          The copy only retains rows whose ids occur in provided row ids.
          The parameter must have been initialized on this context before.
  
          Parameters
          ----------
          row_id: NDArray
              Row ids to retain for the 'row_sparse' parameter.
  
          Returns
          -------
          NDArray on row_id's context