code: def file_prepender(filename):
      
      with open_file(filename, 'r+') as f:
          content = f.read()
          f.seek(0, 0)
          f.write(molecule_prepender(content))
docs: Prepend an informational header on files managed by Molecule and returns
      None.
  
      :param filename: A string containing the target filename.
      :return: None