code: def test_return_type(knn_test_data):
      imputed = impy.fast_knn(knn_test_data)
      return_na_check(imputed)
  
imports: import functools
  import numpy
  import impyute
  from impyute.ops.testing import return_na_check
label_desc: Use image node_id 1 for calling a global function with example usage: test_return_type(knn_test_data) without return types