Removing optimization to be moved into nargsort

Author: brandonmburroughs

pandas/core/series.py

@@ -1788,13 +1788,6 @@ def sort_index(self, axis=0, level=None, ascending=True, inplace=False,
         else:
             from pandas.core.groupby import _nargsort
 
-            if ((ascending and index.is_monotonic_increasing) or
-                    (not ascending and index.is_monotonic_decreasing)):
-                if inplace:
-                    return
-                else:
-                    return self.copy()
-
             indexer = _nargsort(index, kind=kind, ascending=ascending,
                                 na_position=na_position)
             new_index = index.take(indexer)