private def withModifier(req: Requirement): Parser[Any] = {
    if(req.isInstanceOf[DegreeRequirement]) {
    err("_with_ modifiers may not be applied to Degree requirements")
    } |
    (("with"~>determiner)^^{
    //In here I would like to check if req isInstanceOf[RelationshipRequirement]
    //If it is, I would then like to do case d => req.asInstanceOf[RelationshipRequirement].related = d.provtype
    }) |
    ("with"~>"probability"~>numericLit^^{
      case p => req.probability = p.toDouble
    })
}