Set one or more label elements based on
        at least one of the others

def set_label_elements(self, wanted_label_elements):
        """
        Set one or more label elements based on
        at least one of the others
        """
        if isinstance(wanted_label_elements, str):
            wanted_label_elements = [wanted_label_elements]

        # Figure out which desired label elements are missing
        missing_elements = [e for e in wanted_label_elements if getattr(self, e) is None]

        contained_elements = [e for e in ann_label_fields if getattr(self, e )is not None]

        if not contained_elements:
            raise Exception('No annotation labels contained in object')

        for e in missing_elements:
            self.convert_label_attribute(contained_elements[0], e)

        unwanted_label_elements = list(set(ann_label_fields)
                                       - set(wanted_label_elements))

        self.rm_attributes(unwanted_label_elements)

        return