update from Atlas repo

sequences/sentence.py

@@ -17,5 +17,8 @@ class Sentence:
     def __getitem__(self, index):
         return self.words[index]  # <2>
 
+    def __len__(self, index):  # <3>
+        return len(self.words)
+
     def __repr__(self):
-        return 'Sentence(%s)' % reprlib.repr(self.text)  # <3>
+        return 'Sentence(%s)' % reprlib.repr(self.text)  # <4>

sequences/sentence_slice.py

@@ -34,6 +34,9 @@ class SentenceSlice:
         else:
             return self.words[position]
 
+    def __len__(self, index):
+        return len(self.words)
+
     # helper functions -- implementation detail
     def _handle_defaults(self, position):
         """handle missing or overflow/underflow start/stop"""