CLN: breaks line to avoid 81 char length

Author: deniederhut

pandas/core/generic.py

@@ -1907,7 +1907,8 @@ def _slice(self, slobj, axis=0, kind=None):
         return result
 
     def _set_item(self, key, value):
-        if isinstance(key, string_types) and callable(getattr(self, key, None)):
+        if (isinstance(key, string_types)
+            and callable(getattr(self, key, None))):
             warnings.warn("Column name '{key}' collides with a built-in "
                           "method, which will cause unexpected attribute "
                           "behavior".format(key=key), stacklevel=3)