I'm trying to write a QGIS processing script using the new API (3.4), but I hardly find any documentation. Based on this excellent resource by Anita Graser (https://anitagraser.com/2018/03/25/processing-script-template-for-qgis3/), I could manage to set up a basic script that mostly fits my needs.

But I have some fixed-value (eg: ['walking', 'car']) options for which I'd like to include drop-down menus. I assume that I have to use a QgsProcessingParameterString but using the available documentation, I could'nt figure out how to do it.