# File lib/mail/parsers/rfc2822.rb, line 2219
    def _nt_group
      start_index = index
      if node_cache[:group].has_key?(index)
        cached = node_cache[:group][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      i0, s0 = index, []
      r1 = _nt_display_name
      s0 << r1
      if r1
        if has_terminal?(":", false, index)
          r2 = instantiate_node(SyntaxNode,input, index...(index + 1))
          @index += 1
        else
          terminal_parse_failure(":")
          r2 = nil
        end
        s0 << r2
        if r2
          i4 = index
          r5 = _nt_mailbox_list_group
          if r5
            r4 = r5
          else
            r6 = _nt_CFWS
            if r6
              r4 = r6
            else
              @index = i4
              r4 = nil
            end
          end
          if r4
            r3 = r4
          else
            r3 = instantiate_node(SyntaxNode,input, index...index)
          end
          s0 << r3
          if r3
            if has_terminal?(";", false, index)
              r7 = instantiate_node(SyntaxNode,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure(";")
              r7 = nil
            end
            s0 << r7
            if r7
              r9 = _nt_CFWS
              if r9
                r8 = r9
              else
                r8 = instantiate_node(SyntaxNode,input, index...index)
              end
              s0 << r8
            end
          end
        end
      end
      if s0.last
        r0 = instantiate_node(SyntaxNode,input, i0...index, s0)
        r0.extend(Group0)
      else
        @index = i0
        r0 = nil
      end

      node_cache[:group][start_index] = r0

      r0
    end