code: def test_impute_value_custom_idw(test_data):
      """fast_knn using custom idw"""
      data = test_data(SHAPE, 0, 2)
      idw_fn = functools.partial(
          impy.ops.inverse_distance_weighting.shepards, power=1
      )
      imputed = impy.fast_knn(data, k=2, idw_fn=idw_fn)
      assert np.isclose(imputed[0, 2], 8.913911092686593)
  
imports: import functools
  import numpy
  import impyute
  from impyute.ops.testing import return_na_check
label_desc: Use image node_id 3 for calling a global function with example usage: test_impute_value_custom_idw(test_data) without return types