Add an example in the doc-string.

Author: gcaria

pandas/core/frame.py

@@ -5651,6 +5651,16 @@ class  max_speed
         2    lion  mammal       80.5
         3  monkey  mammal        NaN
 
+        Using the `names` parameter, it is possible to choose a name for
+        the old index column:
+
+        >>> df.reset_index(names='name')
+             name   class  max_speed
+        0  falcon    bird      389.0
+        1  parrot    bird       24.0
+        2    lion  mammal       80.5
+        3  monkey  mammal        NaN
+
         We can use the `drop` parameter to avoid the old index being added as
         a column: