revert

Author: MarcoGorelli

pandas/io/parsers/base_parser.py

@@ -1234,9 +1234,7 @@ def _isindex(colspec):
                     continue
                 # Pyarrow engine returns Series which we need to convert to
                 # numpy array before converter, its a no-op for other parsers
-                inp = np.asarray(data_dict[colspec])
-                res = converter(inp)
-                data_dict[colspec] = res
+                data_dict[colspec] = converter(np.asarray(data_dict[colspec]))
             else:
                 new_name, col, old_names = _try_convert_dates(
                     converter, colspec, data_dict, orig_names