code: def test_agg_metadata(self, name, agg_func, exp_type, corpus):
      result = corpus.agg_metadata(name, agg_func)
      assert isinstance(result, exp_type)
  
imports: import collections
  import itertools
  import numpy
  import pytest
  from spacy.tokens import Doc
  from textacy import Corpus
  from textacy import load_spacy_lang
label_desc: Use image node_id 1 for calling the TestCorpusMethods obj's underlying member method code with example usage: obj.test_agg_metadata(name, agg_func, exp_type, corpus) without return types