The semicolon does nothing in the code you show.
I suspect this is someone who programs in another language (C, Java, …) that requires semicolons at the end of statements and it’s just a habit (happens to me sometimes too).
If you want to put several Python statements on the same line, you can use a semi-colon to separate them, see this Python Doc:
A suite is a group of statements controlled by a clause. A suite can
be one or more semicolon-separated simple statements on the same line
as the header, following the header’s colon, or it can be one or more
indented statements on subsequent lines