code: def to_dict(keys):
      return {key: None for key in keys}
  
imports: from copy import deepcopy
  import pytest
  from nbformat.v4.nbbase import new_code_cell, new_notebook
  from jupytext import reads, writes
  from jupytext.cli import jupytext
  from jupytext.compare import compare, compare_notebooks
  from jupytext.metadata_filter import filter_metadata, metadata_filter_as_dict
label_desc: Use image node_id 1 for calling a global function with example usage: to_dict(keys) and returns: unknown