code: def check_active_cell(ext, active_dict):
      text = ("" if ext == ".py" else HEADER[ext]) + active_dict[ext]
      nb = jupytext.reads(text, ext)
      assert len(nb.cells) == 1
      compare(jupytext.writes(nb, ext), text)
      cell = NotebookNode(active_dict[".ipynb"])
      compare_cells(nb.cells, [cell], compare_ids=False)
  
file_path: jupytext/tests/functional/others/test_active_cells.py
imports: import pytest
  from nbformat import NotebookNode
  import jupytext
  from jupytext.compare import compare, compare_cells
label_desc: Use image node_id 1 for calling a global function with example usage: check_active_cell(ext, active_dict) without return types