How to use the yamlpath.func.append_list_element function in yamlpath

def test_anchorless_list_element_error(self):
        with pytest.raises(ValueError) as ex:
            append_list_element({}, YAMLPath("foo"), "bar")
        assert -1 < str(ex.value).find("Impossible to add an Anchor")

("Processor::_get_optional_nodes:  Element <{}>{} is"
                     + " unknown in the data!  Applying default, <{}>{}."
                    ).format(segment_type, except_segment, type(value), value)
                )
                if isinstance(data, list):
                    self.logger.debug(
                        "Processor::_get_optional_nodes:  Dealing with a list"
                    )
                    if (
                            segment_type is PathSegmentTypes.ANCHOR
                            and isinstance(stripped_attrs, str)
                    ):
                        next_node = build_next_node(
                            yaml_path, depth + 1, value
                        )
                        new_ele = append_list_element(
                            data, next_node, stripped_attrs
                        )
                        for node_coord in self._get_optional_nodes(
                                new_ele, yaml_path, value, depth + 1,
                                data, len(data) - 1
                        ):
                            matched_nodes += 1
                            yield node_coord
                    elif (
                            segment_type in [
                                PathSegmentTypes.INDEX,
                                PathSegmentTypes.KEY]
                    ):
                        if isinstance(stripped_attrs, int):
                            newidx = stripped_attrs
                        else:

else:
                            try:
                                newidx = int(str(stripped_attrs))
                            except ValueError:
                                raise YAMLPathException(
                                    ("Cannot add non-integer {} subreference"
                                     + " to lists")
                                    .format(str(segment_type)),
                                    str(yaml_path),
                                    except_segment
                                )
                        for _ in range(len(data) - 1, newidx):
                            next_node = build_next_node(
                                yaml_path, depth + 1, value
                            )
                            append_list_element(data, next_node)
                        for node_coord in self._get_optional_nodes(
                                data[newidx], yaml_path, value,
                                depth + 1, data, newidx
                        ):
                            matched_nodes += 1
                            yield node_coord
                    else:
                        raise YAMLPathException(
                            "Cannot add {} subreference to lists"
                            .format(str(segment_type)),
                            str(yaml_path),
                            except_segment
                        )
                elif isinstance(data, dict):
                    self.logger.debug(
                        "Processor::_get_optional_nodes:  Dealing with a"