code: def test_empty_columns(df):
      df["c"] = np.nan
      res = Description(df)
      dropped = res.frame.c.dropna()
      assert dropped.shape[0] == 2
      assert "missing" in dropped
      assert "nobs" in dropped
  
      df["c"] = np.nan
      res = Description(df.c)
      dropped = res.frame.dropna()
      assert dropped.shape[0] == 2
  
file_path: statsmodels/statsmodels/stats/tests/test_descriptivestats.py
imports: import numpy
  from numpy.testing import assert_almost_equal, assert_equal
  import pandas
  import scipy.stats
  import pytest
  from statsmodels.iolib.table import SimpleTable
  from statsmodels.stats.descriptivestats import Description, describe, sign_test
label_desc: Use image node_id 9 for calling a global function with example usage: test_empty_columns(df) without return types