mypy telling Value of type "PdfObject" is not indexable

[rassie]

I'm moving from PyPDF2 1.x to current pypdf and also trying to use typings in the process. At one point, I need to look into /OCProperties dictionary and I try the following (assuming I have a PdfReader instance from earlier):

root = reader.trailer[TrailerKeys.ROOT]
properties = root[CatalogDictionary.OC_PROPERTIES]

This code works as expected, however, mypy 1.5.1 doesn't like the second line and tells me Value of type "PdfObject" is not indexable. From what I've seen so far, pypdf uses more or less the same code in several places and mypy does not complain.

Any idea why I could be seeing this?

[pubpub-zz]

the annotation of the get([ ]) of a DictionaryObject such as trailer indicates the generic common type PdfObject, to prevent errors, you need to cast it to the adequate type):
root = cast(DictionaryObject,reader.trailer[TrailerKeys.ROOT])
you may neeed to add a global from pypdf.generic import *

[rassie]

Thanks! I thought PdfObject was a descendant of DictionaryObject, but apparently it's not.