code: def test_docstring_with_quadruple_quote(
      nb=new_notebook(
          cells=[
              new_code_cell(
                  '''def fun_1(df):
    """"
    docstring starting with 4 double quotes and ending with 3
    """
    return df'''
              ),
              new_code_cell(
                  '''def fun_2(df):
    """
    docstring
    """
    return df'''
              ),
          ]
      )
  ):
      """Reproduces https://github.com/mwouts/jupytext/issues/460"""
      py = jupytext.writes(nb, "py:percent")
      nb2 = jupytext.reads(py, "py")
      compare_notebooks(nb2, nb)
  
imports: import os
  import pytest
  from nbformat.v4.nbbase import new_code_cell, new_markdown_cell, new_notebook, new_raw_cell
  import jupytext
  from jupytext.compare import compare, compare_notebooks, notebook_model
label_desc: Use image node_id 21 for calling a global function with example usage: test_docstring_with_quadruple_quote(nb) without return types