((parent.isSizer and not isinstance(xxx, xxxSizerItem)) or \
(isinstance(parent, xxxNotebook) and not isinstance(xxx, xxxNotebookPage)) or \
not (parent.isSizer or isinstance(parent, xxxNotebook))):
((parent.isSizer and not isinstance(xxx, xxxSizerItem)) or \
(isinstance(parent, xxxNotebook) and not isinstance(xxx, xxxNotebookPage)) or \
not (parent.isSizer or isinstance(parent, xxxNotebook))):