code: def test_no_metadata_when_py_is_pep8(py_file):
      """This test assumes that all Python files in the jupytext folder follow PEP8 rules"""
      nb = read(py_file)
  
      for i, cell in enumerate(nb.cells):
          if "title" in cell.metadata:
              cell.metadata.pop("title")  # pragma: no cover
          if i == 0 and not cell.source:
              assert cell.metadata == {
                  "lines_to_next_cell": 0
              }, py_file  # pragma: no cover
          else:
              assert not cell.metadata, (py_file, cell.source)
  
file_path: jupytext/tests/unit/test_pep8.py
imports: from nbformat.v4.nbbase import new_code_cell, new_notebook
  from jupytext import read, reads, writes
  from jupytext.compare import compare
  from jupytext.pep8 import cell_ends_with_code, cell_ends_with_function_or_class, cell_has_code, next_instruction_is_function_or_class, pep8_lines_between_cells
label_desc: Use image node_id 9 for calling a global function with example usage: test_no_metadata_when_py_is_pep8(py_file) without return types