ReadonlychildrenNested outline items linked through the First/Last hierarchy.
ReadonlydestDestination from the outline item's Dest entry or Go-To action, or
null if it has none. See ISO 32000-2:2020, 12.3.3, Table 151 and
12.6.4.2, Table 202.
ReadonlytitleHuman-readable label from the outline item's Title entry.
A node of the document outline (a.k.a. bookmarks), corresponding to an outline item dictionary in ISO 32000-2:2020, 12.3.3, Table 151.