def create(proto, *args)
      options = args.last.is_a?(Hash) ? args.pop : {}
      raise ArgumentError, "proto #{proto} must be protocol" unless proto.is_a?(Protocol)
      raise ArgumentError, "command structure mismatch" if !options.empty? && structure.instance_of?(RLP::Sedes::CountableList)
      options.empty? ? args : options
    end
def create(proto, *args)
      options = args.last.is_a?(Hash) ? args.pop : {}
      raise ArgumentError, "proto #{proto} must be protocol" unless proto.is_a?(Protocol)
      raise ArgumentError, "command structure mismatch" if !options.empty? && structure.instance_of?(RLP::Sedes::CountableList)
      options.empty? ? args : options
    end
optionally implement create