I am trying to find the best way to evaluate if OBX-3 = ^IS TEST PATIENT? and OBX-5 =  Y In the same OBX in a Business Rule

OBX|1|NM|P-CSN|1|7623201922192||||||F
OBX|2|NM|P-UCI|2|||||||F
OBX|3|TX|^ADT: PATIENT CLASS|1|Outpatient|||||||||20210715
OBX|4|TX|^IS TEST PATIENT?|1|Y

I started to create a function in a class that uses the Rule [] bracket syntax and  extends  Ens.Rule.FunctionSet:

But after some initial troubleshooting I realized that the [] brackets will not return a value if a field is null, making the two lists different lengths and impossible to compare.

HL7.