def visit_nonterminal(nonTerminalNd)
      broadcast(:before_non_terminal, nonTerminalNd)
      unless nonTerminalNd.signature_exist?
        nonTerminalNd.add_edge_signatures(prime_enum)
      end
      traverse_children(nonTerminalNd)
      broadcast(:after_non_terminal, nonTerminalNd)
    end
def visit_nonterminal(nonTerminalNd)
      broadcast(:before_non_terminal, nonTerminalNd)
      unless nonTerminalNd.signature_exist?
        nonTerminalNd.add_edge_signatures(prime_enum)
      end
      traverse_children(nonTerminalNd)
      broadcast(:after_non_terminal, nonTerminalNd)
    end
Visit event. The visitor is about to visit the given non terminal node.
 @param nonTerminalNd [NonTerminalNode] the node to visit.