code: def test_read_only_validator(self):
      validator = validators.ReadOnly()
      assert (
          validator(self.form_mock, self.form_read_only_field_mock)
          is None
      )
      assert self.form_read_only_field_mock.flags.readonly is True
  
imports: from __future__ import annotations
  from unittest import mock
  import pytest
  from airflow.www import validators
label_desc: Use image node_id 2 for calling the TestReadOnly obj's underlying member method code with example usage: obj.test_read_only_validator() without return types