code: def test_ngrams(n, separator, expected_values):
      strings = cudf.Series(
          [
              "this",
              "is",
              "my",
              "favorite",
              "book",
              "on",
              "my",
              "bookshelf",
          ]
      )
  
      expected = cudf.Series(expected_values)
  
      actual = strings.str.ngrams(n=n, separator=separator)
  
      assert type(expected) == type(actual)
      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 8 for calling a global function with example usage: test_ngrams(n, separator, expected_values) without return types