Simple filter expression is also an array. It contains one or more filter terms, combined with operators - 'AND', 'OR', 'NOT'. (Operators are case insensitive):
[
['mainline', 'is', 'T'],
'and', ['type','anyof',['CustInvc','CustCred']],
'and', 'not', ['amount', 'equalto', '0.00'],
'or'...