code: def _preprocess(self, data):
      if not hasattr(data, "gf") or data["gf"] is None:
          data.gf = torch.FloatTensor([[]])
  
file_path: AutoGL/autogl/module/_feature/graph/base.py
imports: from ..base import BaseFeature
  import numpy
  import torch
  from ..None import register_feature
label_desc: Use image node_id 2 for calling the BaseGraph obj's underlying member method code with example usage: obj._preprocess(data) without return types