Whitelist requirement rule which extends another requirement should allow duplicates

Let's say there is a requirement:

requirement: {
rule_id: 'a'
whitelist: 'something'
}

If there is a rule which extends it with the same whitelist, the compiler will throw an error:

requirement {
extends: 'a'
whitelist: 'something'
}

Result: Invalid requirement. Reason: duplicate whitelist value: something
Expected result: no error should be thrown in this case.