fix bug which broke alignment

rabernat · rabernat · commit 68f170ceea4d · 2018-09-10T14:08:50.000-04:00
diff --git a/xarray/core/coordinates.py b/xarray/core/coordinates.py
@@ -307,7 +307,7 @@ def __len__(self):
         return sum(self._is_index_variable(key) for key in self._sizes)
 
     def __contains__(self, key):
-        self._is_index_variable(key)
+        return self._is_index_variable(key)
 
     def __getitem__(self, key):
         if not self._is_index_variable(key):
