code: def test_insert_mask_before_placeholder(self):
      insert_mask_before_placeholder_cls = get_transforms_cls(
          ["insert_mask_before_placeholder"]
      )["insert_mask_before_placeholder"]
      opt = Namespace(**self.base_opts)
      insert_mask_before_placeholder_transform = (
          insert_mask_before_placeholder_cls(opt)
      )
      ex_in = {
          "src": "### Instruction: ｟newline｠instruction｟newline｠｟newline｠"
          "### Response : ｟newline｠response",
          "tgt": "",
      }
      ex_in["src"] = ex_in["src"].split(" ")
      ex_in["tgt"] = ex_in["src"]
      ex_out = insert_mask_before_placeholder_transform.apply(ex_in)
      ex_gold = {
          "src": [
              "###",
              "Instruction:",
              "｟newline｠instruction｟newline｠｟newline｠###",
              "Response",
              ":",
              "｟newline｠｟_mask_before_｠response",
          ],
          "tgt": [
              "###",
              "Instruction:",
              "｟newline｠instruction｟newline｠｟newline｠###",
              "Response",
              ":",
              "｟newline｠｟_mask_before_｠response",
          ],
      }
      self.assertEqual(ex_out, ex_gold)
  
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 2 for calling the TestInsertMaskBeforePlaceholder obj's underlying member method code with example usage: obj.test_insert_mask_before_placeholder() without return types