aws glue apply_mapping does not throw an error

Question

Hi i have dynamic_frame with data like this.

+---------+-----+
| url link|count|
+---------+-----+
| link1   |    2|
| link2   |    2|
+---------+-----+

Then i apply mapping like df.apply_mapping(['url_link','string','url_link','string'])

Column name has space insead of underscore but glue job is not failing and all data from 'url link' comes to 'url_link' at new dataframe. Is it expected behaviour? Does anyone know how it works?