code: def test_mask(self):
      # test does the mask label work
      new = ner_sample.insert_field_after_index("text", 0, "abc")
      new = new.delete_field_at_index("text", 1)
      # TODO wait repair bug
      print(new.dump())
      print(new.text.mask)
  
file_path: textflint/test/input/component/sample/test_ner_sample.py
imports: import unittest
  from textflint.input.component.sample.ner_sample import *
label_desc: Use image node_id 8 for calling the TestNERSample obj's underlying member method code with example usage: obj.test_mask() without return types