Understanding a line in issue.item.html

Hello Everyone,

I struggle to understand a line in issue.item.html (based on the classic tracker template).

I duplicated everything for keywords (renamed to projects), but the filter statement eludes me:
- here is a link to the codeline https://codeberg.org/R2D2/roundup_todo_tracker_template/src/commit/e9eb1610830f8c188de1bfa0c6fbd8d560739d84/todo/html/issue.item.html#L79
- I want to extend this with a second keyword field named project
- Is there a way to use something like an format-string within the filter='...' expression?


Thanks in advance!


--
Have a fine week!

r2d2