code: def test_nan_exists():
      """If no NaN, BadInputError raised"""
      with pytest.raises(error.BadInputError) as excinfo:
          some_fn(np.array([[1.0]]))
      assert str(excinfo.value) == "No NaN's in given data"
  
imports: import pytest
  import numpy
  from impyute.imputation.cs import mean
  from impyute.ops import error
  from impyute.ops import wrapper
label_desc: Use image node_id 9 for calling a global function with example usage: test_nan_exists() without return types