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* Fix the error when calling :meth:`.to_item() <web_poet.pages.ItemPage.to_item>`,
:func:`item_from_fields_sync() <web_poet.fields.item_from_fields_sync>`, or
:func:`item_from_fields() <web_poet.fields.item_from_fields>` on page objects
defined as slotted attrs classes, while setting ``skip_nonitem_fields=True``.