code: def notebook_model(nb):
      """Return a notebook model, with content a
      dictionary rather than a notebook object.
      To be used in tests only."""
      return dict(type="notebook", content=json.loads(json.dumps(nb)))
  
imports: import difflib
  import json
  import os
  import re
  from jupytext.paired_paths import full_path
  from .cell_metadata import _IGNORE_CELL_METADATA
  from .combine import combine_inputs_with_outputs
  from .formats import check_auto_ext, long_form_one_format
  from .header import _DEFAULT_NOTEBOOK_METADATA
  from .jupytext import read, reads, write, writes
  from .metadata_filter import filter_metadata
label_desc: Use image node_id 11 for calling a global function with example usage: notebook_model(nb) and returns: dict