code: def test_group_stats_calc_stats(df):
      gs = df.calc_stats()
  
      num_stats = len(gs.stats.index)
      num_unique_stats = len(gs.stats.index.drop_duplicates())
      assert num_stats == num_unique_stats
  
imports: import ffn
  import pandas
  import numpy
  from pytest import fixture
  from numpy.testing import assert_almost_equal
label_desc: Use image node_id 42 for calling a global function with example usage: test_group_stats_calc_stats(df) without return types