code: def _format_lineno(session, line):
      """Helper function to format line numbers properly."""
      if session == 0:
          return str(line)
      return "%s#%s" % (session, line)
  
imports: from __future__ import print_function
  import atexit
  import datetime
  import os
  import re
  import threading
  from traitlets.config.configurable import LoggingConfigurable
  from decorator import decorator
  from IPython.utils.decorators import undoc
  from IPython.paths import locate_profile
  from IPython.utils import py3compat
  from traitlets import Any, Bool, Dict, Instance, Integer, List, Unicode, TraitError, default, observe
  from warnings import warn
label_desc: Use image node_id 4 for calling a global function with example usage: _format_lineno(session, line) and returns: unknown, str