code: def row(self):
      row = self._row
      if row is not None:
          return row
  
      rowptr = self._rowptr
      if rowptr is not None:
          row = torch.ops.torch_sparse.ptr2ind(
              rowptr, self._col.numel()
          )
          self._row = row
          return row
  
      raise ValueError
  
imports: import warnings
  from typing import List, Optional, Tuple
  import torch
  from torch_scatter import scatter_add, segment_csr
  from torch_sparse.utils import Final, index_sort
label_desc: Use image node_id 4 for calling the SparseStorage obj's underlying member method code with example usage: obj.row() and returns: row, row