Fix a forgotten import in NGrams

GEODE/Classification/NGrams.py

@@ -2,6 +2,7 @@ from GEODE.Metadata import articleKey, toKey
 from GEODE.Classification.Stopwords import isStopWord
 from GEODE.Store import tabular
 import nltk
+import pandas
 from string import punctuation
 
 tools = {'lemmatize': None, 'spacyFr': None}