Is it possible to match no priority

Questions & Help
1

I am looking to find tasks with no priority (since this is the default priority when using the /todo command to create a task)
To find certain priorities I use [(contains? #{"A" "B" "C" "a" "b" "c" "0" "1" "2" "3"} ?priority)] and I am hoping there is a way to use some sort of “NOT” boolean operator to match tasks with null priority

2

Something like this:

[?b :block/marker]
(not [?b :block/priority])
3

I used
(not (priority A B C))
until now.