class_docstr: - Use ROUGE-2 as [PaLM 2](https://ai.google/static/documents/palm2techreport.pdf)
  - Use Mecab tokenizer for Japanese eval
code: def higher_is_better(self):
      return {
          "rouge2": True,
      }
  
imports: import os
  import inspect
  from lm_eval.utils import rouge2_mecab
  from lm_eval.base import rf, Task
label_desc: Use image node_id 15 for calling the XLSumJa obj's underlying member method code with example usage: obj.higher_is_better() and returns: dict