code: def _serialize_single_file(uploaded_file):
      js = {}
      for attribute in ["name", "type", "size", "content"]:
          js[attribute] = uploaded_file[attribute]
      js["last_modified"] = int(
          uploaded_file["last_modified"].timestamp() * 1000
      )
      return js
  
file_path: catboost/contrib/python/ipywidgets/py3/ipywidgets/widgets/widget_upload.py
imports: import datetime
  from traitlets import observe, default, Unicode, Dict, Int, Bool, Bytes, CaselessStrEnum
  from .widget_description import DescriptionWidget
  from .valuewidget import ValueWidget
  from .widget_core import CoreWidget
  from .widget_button import ButtonStyle
  from .widget import register, widget_serialization
  from .trait_types import InstanceDict, TypedTuple
  from traitlets import Bunch
label_desc: Use image node_id 3 for calling a global function with example usage: _serialize_single_file(uploaded_file) and returns: js