How to exclude list from list

Hi

How can we exclude/substract a list from another list with mistral (yaql) and orquestra?

L1=[ 'a', 'b', 'c' ]
L2= [ 'a' ]

I want
L3= L1-L2= [ 'b', 'c' ]

I tried with set but st2 Can not evaluate YAQL expression:

res: <% list(set(L1) - set(L2)) %>

Stackstormly

Follow the YAQL documentation which has this functionality covered https://yaql.readthedocs.io/en/latest/standard_library.html#working-with-collections