If a CombinedFragment operator is of type ‘opt’, ‘loop’, ‘break’ or ‘neg’ there should be only one InteractionOperand in this CombinedFragment.

The ‘opt’, ‘loop’, ‘break’ and ‘neg’ operators are defined to work with only one operand.

This rule indicates an inconsistency between the operator and the number of InteractionOperand in the CombinedFragment in question.