I found, the filter actually has to be an iterable:
Task.get_tasks(project_name="my-project", task_name="my-task", task_filter=dict(type=["training"])))

AgitatedDove14 How can I filter out tasks archived? I don't see this option

yes, so you can have a few options 🙂

JitteryCoyote63 to filter out 'archived tasks' (i.e. exclude archived tasks)
Task.get_tasks(project_name="my-project", task_name="my-task", task_filter=dict(system_tags=["-archived"])))

Thanks!