code: def nacnt():
      fr = h2o.import_file(
          pyunit_utils.locate("smalldata/logreg/prostate.csv")
      )
      nacnts1 = fr.nacnt()
      assert all([i == 0 for i in nacnts1])
      fr.insert_missing_values()
      nacnts2 = fr.nacnt()
      assert all([i > 0 for i in nacnts2])
  
label_desc: Use image node_id 1 for calling a global function with example usage: nacnt() without return types