Method get_importance_of_reason

returns, how important the 'to' node is if all types are equal, sorting will be done by this importance for example, when we are searching for why $a is float, and we have { $a = 4.5; $a = $v; } and $v is float, then $v is a more important reason than 4.5, as we want to see, why $v also occurred float, not just stop at 4.5 so, a variable is more important than a constant, a func call is more impor