code: def test_raw_string_is_stable_over_round_trip(r, triple_quote, expr):
      py = f"""# %% [markdown]
  {r}{triple_quote}
  A {expr} expression
  {triple_quote}
  """
  
      nb = jupytext.reads(py, "py:percent")
  
      (cell,) = nb.cells
      assert cell.cell_type == "markdown"
      assert cell.source == f"A {expr} expression"
      assert cell.metadata["cell_marker"] == f"{r}{triple_quote}"
  
      py2 = jupytext.writes(nb, "py:percent")
      compare(py2, py)
  
imports: import pytest
  from nbformat.v4.nbbase import new_markdown_cell, new_notebook
  import jupytext
  from jupytext.compare import compare
label_desc: Use image node_id 2 for calling a global function with example usage: test_raw_string_is_stable_over_round_trip(r, triple_quote, expr) without return types