Change _values to _ndarray_values in drop_duplicates

Author: makbigc

pandas/core/frame.py

@@ -4624,7 +4624,7 @@ def drop_duplicates(self, subset=None, keep='first', inplace=False):
         duplicated = self.duplicated(subset, keep=keep)
 
         if inplace:
-            inds, = (-duplicated)._values.nonzero()
+            inds, = (-duplicated)._ndarray_values.nonzero()
             new_data = self._data.take(inds)
             self._update_inplace(new_data)
         else: