ontology load error

[Ali-MH-Mansour]

Hi
Thanks for this work.
I got an error msg when loading ontology. i used the following code
pip install pytrips
pip install pytrips[tools] # optional
import nltk
nltk.download('wordnet')

from pytrips.ontology import load
ont = load()
KeyError: 'restriction' line 45 in ontology.py

i think it should be restr?