code: def test_transform_specials(self):
      transforms_cls = get_transforms_cls(["prefix"])
      corpora = yaml.safe_load(
          """
              trainset:
                  path_src: data/src-train.txt
                  path_tgt: data/tgt-train.txt
                  transforms: ["prefix"]
                  weight: 1
                  src_prefix: "｟_pf_src｠"
                  tgt_prefix: "｟_pf_tgt｠"
          """
      )
      opt = Namespace(data=corpora)
      specials = get_specials(opt, transforms_cls)
      specials_expected = {"src": ["｟_pf_src｠"], "tgt": ["｟_pf_tgt｠"]}
      self.assertEqual(specials, specials_expected)
  
imports: import unittest
  import copy
  import yaml
  import math
  from argparse import Namespace
  from onmt.transforms import get_transforms_cls, get_specials, make_transforms, TransformPipe
  from onmt.transforms.bart import BARTNoising
label_desc: Use image node_id 3 for calling the TestTransform obj's underlying member method code with example usage: obj.test_transform_specials() without return types