code: def aggregation(self):
      return {
          "rouge2": self._rouge,
      }
  
imports: import os
  import numpy
  import datasets
  from lm_eval.base import rf, Task
  from lm_eval.metrics import mean
  from lm_eval.utils import rouge2_mecab
label_desc: Use image node_id 13 for calling the Wikilingua obj's underlying member method code with example usage: obj.aggregation() and returns: dict