code: def test_insert_field_before_index(self):
      # test insert before index and mask
      ins_bef = wsc_sample.insert_field_before_index("text", 0, "[cls]")
      self.assertEqual(
          "[cls] The city councilmen refused the demonstrators a permit because "
          "they feared violence.",
          ins_bef.dump()["text"],
      )
      self.assertEqual(
          ins_bef.dump()["target"],
          {
              "noun1": "The city councilmen",
              "noun2": "The demonstrators",
              "noun1_idx": 1,
              "noun2_idx": 5,
              "pron": "they",
              "pron_idx": 10,
          },
      )
  
file_path: textflint/test/input/component/sample/test_wsc_sample.py
imports: import unittest
  from textflint.input.component.sample.wsc_sample import *
label_desc: Use image node_id 3 for calling the TestWSCSample obj's underlying member method code with example usage: obj.test_insert_field_before_index() without return types