Article History
Received: 15 May 2019
Accepted: 30 December 2019
First Online: 15 January 2020
Change Date: 31 January 2020
Change Type: Update
Change Details: Due to a typesetting error, in the original version of this Article the text “gif” was replaced by “.png”, leading to a typographical error. This has now been fixed in the Article.
Competing interests
: The authors declare no competing interests.