code: def test_metadata_and_cell_to_header2(no_jupytext_version_number):
      nb = new_notebook(
          cells=[new_markdown_cell(source="Some markdown\ntext")]
      )
      header, lines_to_next_cell = metadata_and_cell_to_header(
          nb, {}, get_format_implementation(".md"), {"extension": ".md"}
      )
      assert header == []
      assert len(nb.cells) == 1
      assert lines_to_next_cell is None
  
file_path: jupytext/tests/unit/test_header.py
imports: from nbformat.v4.nbbase import new_markdown_cell, new_notebook, new_raw_cell
  import jupytext
  from jupytext.compare import compare
  from jupytext.formats import get_format_implementation
  from jupytext.header import header_to_metadata_and_cell, metadata_and_cell_to_header, uncomment_line
label_desc: Use image node_id 6 for calling a global function with example usage: test_metadata_and_cell_to_header2(no_jupytext_version_number) without return types