add versionchanged note

Author: reidy-p

pandas/core/generic.py

@@ -4889,6 +4889,9 @@ def bfill(self, axis=None, inplace=False, limit=None, downcast=None):
             The method to use when for replacement, when ``to_replace`` is a
             scalar, list or tuple and ``value`` is None.
 
+        .. versionchanged:: 0.23.0
+           Added to DataFrame
+
         See Also
         --------
         %(klass)s.fillna : Fill NA/NaN values