def visit_alternative(alternativeNd)
      broadcast(:before_alternative, alternativeNd)
      unless alternativeNd.signature_exist?
        alternativeNd.add_edge_signatures(prime_enum)
      end

      traverse_children(alternativeNd)
      broadcast(:after_alternative, alternativeNd)
    end
def visit_alternative(alternativeNd)
      broadcast(:before_alternative, alternativeNd)
      unless alternativeNd.signature_exist?
        alternativeNd.add_edge_signatures(prime_enum)
      end

      traverse_children(alternativeNd)
      broadcast(:after_alternative, alternativeNd)
    end
TODO: control the logic of this method.
 Visit event. The visitor is visiting the
 given alternative node.
 @param alternativeNd [AlternativeNode] the alternative node to visit.