docstr: If train_param_blobs is not set before used, default to param_blobs
docstr_tok: ["If","train_param_blobs","is","not","set","before","used",",","default","to","param_blobs"]
code: def train_param_blobs(self):
      """
      If train_param_blobs is not set before used, default to param_blobs
      """
      if self._train_param_blobs is None:
          self.train_param_blobs = self.param_blobs
      return self._train_param_blobs
  
file_path: pytorch/caffe2/python/layers/sampling_trainable_mixin.py
imports: import abc
label_desc: Use image node_id 3 for calling the SamplingTrainableMixin obj's underlying member method code with example usage: obj.train_param_blobs() and returns: self