code: def create_mirror_file_if_missing(mirror_file, notebook, fmt):
      if not os.path.isfile(mirror_file):
          write(notebook, mirror_file, fmt=fmt)
  
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 9 for calling a global function with example usage: create_mirror_file_if_missing(mirror_file, notebook, fmt) without return types