code: def test_missing_values_present():
      """Check that the dataset is corrupted (missing values present)"""
      assert matrix.nan_indices(data).size != 0
  
imports: import numpy
  import pytest
  from impyute.dataset import mnist
  from impyute.ops import matrix
label_desc: Use image node_id 2 for calling a global function with example usage: test_missing_values_present() without return types