code: def test_header_in_html_comment():
      text = """<!--
  
  ---
  jupyter:
    title: Sample header
  ---
  
  -->
  """
      lines = text.splitlines()
      metadata, _, cell, _ = header_to_metadata_and_cell(lines, "", "")
  
      assert metadata == {"title": "Sample header"}
      assert 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 9 for calling a global function with example usage: test_header_in_html_comment() without return types