code: def h2o_H2OFrame_num_valid_substrings():
      """
      Python API test: h2o.frame.H2OFrame.num_valid_substrings(i)
      """
      try:
          # generate files to write to
          results_dir = pyunit_utils.locate(
              "results"
          )  # real test when result directory is there
          full_path = os.path.join(
              results_dir, "test_num_valid_substrings.txt"
          )
          with open(full_path, "w") as text_file:
              text_file.write("setosa")
              text_file.write("\n")
              text_file.write("virginica")
          iris = h2o.import_file(
              path=pyunit_utils.locate(
                  "smalldata/iris/iris_wheader_NA_2.csv"
              )
          )
          temp = iris[4].num_valid_substrings(path_to_words=full_path)
          assert_is_type(temp, H2OFrame)
          assert (
              temp.sum().flatten() == 100
          ), "h2o.H2OFrame.num_valid_substrings command is not working."
      except Exception as e:
          if "File not found" in e.args[0]:
              print(
                  "Directory is not writable.  h2o.H2OFrame.num_valid_substrings is tested for number of argument "
                  "and argument name only."
              )
              allargs = inspect.getfullargspec(
                  h2o.H2OFrame.num_valid_substrings
              )
              assert (
                  len(allargs.args) == 2
                  and allargs.args[1] == "path_to_words"
              ), "h2o.H2OFrame.num_valid_substrings() contains only one argument, path_to_words!"
          else:
              assert (
                  False
              ), "h2o.H2OFrame.num_valid_substrings() contains only one argument, path_to_words!"
  
imports: import sys, os
  import h2o
  from tests import pyunit_utils
  import inspect
  from h2o.utils.typechecks import assert_is_type
  from h2o.frame import H2OFrame
label_desc: Use image node_id 1 for calling a global function with example usage: h2o_H2OFrame_num_valid_substrings() without return types