Verbnet all lemma list includes NNPs

[tttthomasssss]

The first three items in verbnet.lemmas() are "December", "FedEx" and "UPS" (using NLTK 3.3).

The following is a minimal example to reproduce the issue:

In [3]: import nltk

In [4]: nltk.__version__
Out[4]: '3.3'

In [5]: from nltk.corpus import verbnet

In [6]: verbnet.lemmas()[:10]
Out[6]: 
['December',
 'FedEx',
 'UPS',
 'abandon',
 'abase',
 'abash',
 'abate',
 'abbreviate',
 'abduct',
 'abet']