docstr: Test if the v-head is added to the model successfully, by passing a non `PretrainedModel`
  as an argument to `from_pretrained`.
docstr_tok: ["Test","if","the","v-head","is","added","to","the","model","successfully",",","by","passing","a","non","`","PretrainedModel","`","as","an","argument","to","`","from_pretrained","`","."]
code: def test_value_head_not_str(self):
      r"""
      Test if the v-head is added to the model successfully, by passing a non `PretrainedModel`
      as an argument to `from_pretrained`.
      """
      for model_name in self.all_model_names:
          pretrained_model = (
              self.transformers_model_class.from_pretrained(model_name)
          )
          model = self.trl_model_class.from_pretrained(pretrained_model)
          self.assertTrue(hasattr(model, "v_head"))
  
imports: import gc
  import tempfile
  import unittest
  import torch
  from transformers import AutoModel, AutoModelForCausalLM, AutoModelForSeq2SeqLM
  from trl import AutoModelForCausalLMWithValueHead, AutoModelForSeq2SeqLMWithValueHead, create_reference_model
label_desc: Use image node_id 4 for calling the VHeadModelTester obj's underlying member method code with example usage: obj.test_value_head_not_str() without return types