def METHOD_NAME(self):
    r"""Generates a menu with existing items.
    Parameters
    ----------
    linked : bool, optional
        Indicates whether the actions should result in linked (True) or
        unliked (False) copies.
    Returns
    -------
    QMenu
    """
    self._items = []
    target_item_name = self.target_treeitem.item.name
    for item_name in self.experiment.items:
        if target_item_name in \
                self.experiment.items[item_name].children() or \
                item_name == target_item_name:
            continue
        self._items.append(item_name)
    self._items.sort()
    m = QtWidgets.QMenu(self)
    for item_name in self._items:
        m.addAction(AppendExistingAction(self, m, item_name))
    return m