code: def test_prefix_tokens(self):
      tokenizer = self.tokenizer_class.from_pretrained(
          "Tanrei/GPTSAN-japanese"
      )
  
      x_token_1 = tokenizer.encode("あンいワ")
      x_token_2 = tokenizer.encode("", prefix_text="あンいワ")
      x_token_3 = tokenizer.encode("いワ", prefix_text="あン")
  
      self.assertEqual(
          tokenizer.decode(x_token_1), tokenizer.decode(x_token_2)
      )
      self.assertEqual(
          tokenizer.decode(x_token_1), tokenizer.decode(x_token_3)
      )
      self.assertNotEqual(x_token_1, x_token_2)
      self.assertNotEqual(x_token_1, x_token_3)
      self.assertEqual(x_token_1[1], x_token_2[-1])  # SEG token
      self.assertEqual(x_token_1[1], x_token_3[3])
  
imports: import json
  import os
  import unittest
  from transformers.models.gptsan_japanese.tokenization_gptsan_japanese import VOCAB_FILES_NAMES, GPTSanJapaneseTokenizer
  from transformers.testing_utils import require_jinja, require_tokenizers, slow
  from ...test_tokenization_common import TokenizerTesterMixin
label_desc: Use image node_id 12 for calling the GPTSanJapaneseTokenizationTest obj's underlying member method code with example usage: obj.test_prefix_tokens() without return types