code: def join(left, right, sep):
      if left:
          return left + sep + right
      return right
  
file_path: jupytext/src/jupytext/paired_paths.py
imports: import os
  from .config import find_jupytext_configuration_file
  from .formats import NOTEBOOK_EXTENSIONS, long_form_multiple_formats, long_form_one_format, short_form_multiple_formats, short_form_one_format
label_desc: Use image node_id 2 for calling a global function with example usage: join(left, right, sep) and returns: right, unknown