docs: def write_configuration_file(filepath=_give_default_file_path(),
                               overwrite=False):
      """Create a configuration file.
  
      Writes the current state of settings into a configuration file.
  
      .. note:: Since a file is permamently written, this function
          is strictly speaking not sideeffect free.
  
      Args:
          filepath (str): Where to write the file.
              The default is under both UNIX and Windows ``~/.chemcoordrc``.
          overwrite (bool):
  
      Returns:
          None:
      """
      config = configparser.ConfigParser()
      config.read_dict(settings)
  
      if os.path.isfile(filepath) and not overwrite:
          try:
              raise FileExistsError
          except NameError:  # because of python2
              warn('File exists already and overwrite is False (default).')
      else:
          with open(filepath, 'w') as configfile:
              config.write(configfile)