public static Set<?> getFirstOperandAsRawSet(FieldPredicate<?> p) {
        return Cast.castOrFail(getFirstOperandAsRaw(p), Set.class);
    }
Returns the first operand of the specified {@link FieldPredicate} as
a {@code java.util.Set}, throwing an exception if it doesn't exist or if
it wasn't a {@code Set}. The operand may however be {@code null}.

@param p  the predicate
@return   the operand
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/util/PredicateOperandUtil.java