code: def _check_candidates(candidates: Dict[str, pd.DataFrame]) -> None:
      ref = next(iter(candidates.values()))
      assert all(
          set(c.index) == set(ref.index) for c in candidates.values()
      ), "Candidates have differing indices."
      assert all(
          set(c.columns) == set(ref.columns)
          for c in candidates.values()
      ), "Candidates have differing columns."
  
imports: from typing import Dict
  import numpy
  import pandas
  import scipy.stats
label_desc: Use image node_id 2 for calling a global function with example usage: _check_candidates(candidates) without return types