def _undo_manager_default(self):
        """ Trait initializer. """

        # We make sure the undo package is entirely optional.
        try:
            from apptools.undo.api import UndoManager
        except __HOLE__:
            return None

        return UndoManager()
dataset/ETHPy150Open enthought/pyface/pyface/workbench/workbench.py/Workbench._undo_manager_default