code: def test_npe_string_vec():
      f = h2o.create_frame(string_fraction=1)
      f["C1"].insert_missing_values(1)
      print(f["C1"][0, 0])
  
imports: import pandas
  import h2o
  from tests import pyunit_utils
  from pandas.util.testing import assert_frame_equal
label_desc: Use image node_id 2 for calling a global function with example usage: test_npe_string_vec() without return types