I checked illustrator_ JavaScript_ Scripting_ Reference_ In 2017, only the document bleeding documentbleedoffsetrect can be set, but the bleeding size that has been set in the document cannot be obtained. Is it because the document is incomplete or this method is not provided? Now how can I get the bleeding size of the current document. thank you!

Examples code:
//set bleed
docPreset.documentBleedOffset = [10, 10 10,10];

But there is no way to get the value that has been set