Is PMT_NIL a Valid Dictionary?

[Jeff S]

GNU Radio Version:  v3.9.6.0-23-ge3506b13

I was writing a QA test and decided to try,

self.assertTrue(pmt.is_dict(pmt.PMT_NIL))

and it passes.  I was just wondering if pmt.PMT_NIL is considered a valid 
dictionary object, as opposed to,

my_dict = pmt.make_dict()
self.assertTrue(pmt.is_dict(my_dict))

Just trying to get a better understanding and couldn't find an answer.

Regards,
Jeff