# File lib/cucumber/runtime/support_code.rb, line 56
      def invoke(step_name, multiline_argument=nil)
        multiline_argument = Cucumber::Ast::MultilineArgument.from(multiline_argument)
        # It is very important to leave multiline_argument=nil as a vararg. Cuke4Duke needs it that way. 
        begin
          step_match(step_name).invoke(multiline_argument)
        rescue Exception => e
          e.nested! if Undefined === e
          raise e
        end
      end