Use names property rather than _names in MultiIndex.isin

Author: Douglas Rudd

pandas/core/indexes/multi.py

@@ -2621,7 +2621,7 @@ def _wrap_joined_index(self, joined, other):
     def isin(self, values, level=None):
         if level is None:
             values = MultiIndex.from_tuples(values,
-                                            names=self._names).values
+                                            names=self.names).values
             return algos.isin(self.values, values)
         else:
             num = self._get_level_number(level)