Fixed bug where _word_set was based on train_set, even if train_set

is filelike instead of iterable.

Author: emmyzero

textblob/classifiers.py

@@ -136,7 +136,7 @@ def __init__(self, train_set, feature_extractor=basic_extractor, format=None, **
             self.train_set = self._read_data(train_set, format)
         else:  # train_set is a list of tuples
             self.train_set = train_set
-        self._word_set = _get_words_from_dataset(train_set) #Keep a hidden set of unique words.
+        self._word_set = _get_words_from_dataset(self.train_set) #Keep a hidden set of unique words.
         self.train_features = None
 
     def _read_data(self, dataset, format=None):