input: Write a python function to count the number of occurrences of a given word in a sentence.
  assert count_word_occurrences("I have an apple, and the apple is delicious.", "apple") == 2
  assert count_word_occurrences("Bananas are great, I love bananas!", "bananas") == 2
  assert count_word_occurrences("This sentence has no special word.", "apple") == 0
output: def count_word_occurrences(sentence, word):
      words = sentence.lower().split()
      word = word.lower()
      return words.count(word)