docs: def set_options_from_YAML(self, filename):
          """Load options from a YAML-formated file.
  
          :param str filename: File from which to load the options.
  
          :raise:
              :IOError: If ``filename`` does not exist.
          """
          if not os.path.isfile(filename):
              raise IOError("File {0} not found".format(filename))
          stream = open(filename)
          data_dict = yaml.safe_load(stream)
          self.set_options_from_dict(data_dict, filename)