code: def test_zero_if_file_nonexistent_and_allow_nonexistent(self):
      assert (
          util.path_modification_time("foo", allow_nonexistent=True)
          == 0.0
      )
  
imports: import tempfile
  import unittest
  from unittest.mock import MagicMock, mock_open, patch
  from streamlit.watcher import util
label_desc: Use image node_id 3 for calling the PathModificationTimeTests obj's underlying member method code with example usage: obj.test_zero_if_file_nonexistent_and_allow_nonexistent() without return types