currently I am working to get some color into the timesheet_grid view. But I think it's somehow impossible. I tried to make an custom-addon of the timesheet_grid, so I can inherit the grid_view and after that I change the color of the task_id field with css. I really dont want to make a new custom widget, neither to overwrite the render.js to make it colorful, because I dont have any experience with js at all (and will take time to get into it). So, to get back on my issue: when adding my css to the field as you can see in my code, I always get an error. This error even occures when trying to change the xml in odoo per UI (per source code). I appreciate any help !

Edit: As far as I know it says the view isnt inherited correctly, but this error also appears when editing the view in the source code.

Link to my code and error : https://stackoverflow.com/questions/67785911/error-when-using-css-class-for-grid-view-in-odoo