to_unicode() function missing

[Wombatpm]

Your code makes use of a to_unicode() function. I think this is a holdover from python 2.7 and is no longer required for python 3.X

[summerswallow]

The to_unicode() method is not a method of a standard string library. The object which to_unicode is a method of is an instance of PdfString as part of the pdfrw library which is the correct way to move from the pdfrw string world to the "normal python string" world. This code was written under Python 3.