code: def test_character_tokenize_series():
      sr = cudf.Series(
          [
              "hello world",
              "sdf",
              None,
              (
                  "goodbye, one-two:three~four+five_six@sev"
                  "en#eight^nine heŒŽ‘•™œ$µ¾ŤƠé Ǆ"
              ),
          ]
      )
      expected_values = [
          "h",
          "e",
          "l",
          "l",
          "o",
          " ",
          "w",
          "o",
          "r",
          "l",
          "d",
          "s",
          "d",
          "f",
          "g",
          "o",
          "o",
          "d",
          "b",
          "y",
          "e",
          ",",
          " ",
          "o",
          "n",
          "e",
          "-",
          "t",
          "w",
          "o",
          ":",
          "t",
          "h",
          "r",
          "e",
          "e",
          "~",
          "f",
          "o",
          "u",
          "r",
          "+",
          "f",
          "i",
          "v",
          "e",
          "_",
          "s",
          "i",
          "x",
          "@",
          "s",
          "e",
          "v",
          "e",
          "n",
          "#",
          "e",
          "i",
          "g",
          "h",
          "t",
          "^",
          "n",
          "i",
          "n",
          "e",
          " ",
          "h",
          "e",
          "Œ",
          "Ž",
          "‘",
          "•",
          "™",
          "œ",
          "$",
          "µ",
          "¾",
          "Ť",
          "Ơ",
          "é",
          " ",
          "Ǆ",
      ]
      expected_index = sr.index.repeat(sr.str.len().fillna(0))
      expected = cudf.Series(expected_values, index=expected_index)
  
      actual = sr.str.character_tokenize()
      assert_eq(expected, actual)
  
      sr = cudf.Series([""])
      expected = cudf.Series([], dtype="object")
  
      actual = sr.str.character_tokenize()
      assert_eq(expected, actual)
  
      sr = cudf.Series(["a"])
      expected = cudf.Series(["a"])
  
      actual = sr.str.character_tokenize()
      assert_eq(expected, actual)
  
imports: import random
  import string
  import numpy
  import pytest
  import cudf
  from cudf.core.byte_pair_encoding import BytePairEncoder
  from cudf.core.tokenize_vocabulary import TokenizeVocabulary
  from cudf.testing._utils import assert_eq
label_desc: Use image node_id 12 for calling a global function with example usage: test_character_tokenize_series() without return types