code: def test_copy_file_dirty_not_modified(self, src_dir, dest_dir):
      file = File(
          "test.txt", src_dir, dest_dir, use_directory_urls=False
      )
      file.is_modified = mock.Mock(return_value=False)
      dest_path = os.path.join(dest_dir, "test.txt")
      file.copy_file(dirty=True)
      self.assertPathIsFile(dest_path)
      with open(dest_path, encoding="utf-8") as f:
          self.assertEqual(f.read(), "destination content")
  
imports: import os
  import sys
  import unittest
  from unittest import mock
  from mkdocs.structure.files import File, Files, _sort_files, get_files
  from mkdocs.tests.base import PathAssertionMixin, load_config, tempdir
label_desc: Use image node_id 25 for calling the TestFiles obj's underlying member method code with example usage: obj.test_copy_file_dirty_not_modified(src_dir, dest_dir) without return types