code: def test_receive_single_file(self):
      uploader = FileUpload()
      message = {"value": [FILE_UPLOAD_FRONTEND_CONTENT]}
      uploader.set_state(message)
      assert len(uploader.value) == 1
      (uploaded_file,) = uploader.value
      assert uploaded_file.name == "file-name.txt"
      assert uploaded_file.type == "text/plain"
      assert uploaded_file.size == 20760
      assert uploaded_file.content.tobytes() == b"file content"
      assert uploaded_file.last_modified == dt.datetime(
          2020, 1, 9, 13, 58, 16, 434000, tzinfo=dt.timezone.utc
      )
  
file_path: catboost/contrib/python/ipywidgets/py3/ipywidgets/widgets/tests/test_widget_upload.py
imports: import datetime
  from unittest import TestCase
  from unittest.mock import MagicMock
  from traitlets import TraitError
  from ipywidgets import FileUpload
label_desc: Use image node_id 4 for calling the TestFileUpload obj's underlying member method code with example usage: obj.test_receive_single_file() without return types