question: @ SuppressWarnings ( { "SimplifiableIfStatement" } ) public final boolean isForbiddenByTiers ( String var1 , String var2 ) { if ( var1 . equals ( var2 ) ) { throw new IllegalArgumentException ( ) ; } Integer tier1 = tierMap . get ( var1 ) ; Integer tier2 = tierMap . get ( var2 ) ; if ( ( tier1 == null ) || ( tier2 == null ) ) { return false ; } else if ( tier1 . equals ( tier2 ) && isTierForbiddenWithin ( tier1 ) ) { return true ; } else { return tier1 > tier2 ; } }
target:  Determines whether the edge var1 --> var2 is forbidden by the temporal tiers.