循环结构

# MCP Server
servers:
  benchmark: servers/benchmark
  retriever: servers/retriever
  prompt: servers/prompt
  generation: servers/generation
  evaluation: servers/evaluation
  custom: servers/custom

# MCP Client Pipeline
pipeline:
- benchmark.get_data
- retriever.retriever_init
- generation.generation_init
- retriever.retriever_search
- loop:
    times: 3
    steps:
    - prompt.gen_subq
    - generation.generate:
        output:
          ans_ls: subq_ls
    - retriever.retriever_search:
        input:
          query_list: subq_ls
        output:
          ret_psg: temp_psg
    - custom.merge_passages
- prompt.qa_rag_boxed
- generation.generate
- custom.output_extract_from_boxed
- evaluation.evaluate