input: Write a function to extract the non-vowel words from a given sentence. The function should return a list of words that do not contain any vowel (a, e, i, o, u, A, E, I, O, U) characters.
  assert extract_words("This machine learning project is challenging.")==['This', 'machine', 'learning', 'project', 'is', 'challenging.']
  assert extract_words("Python programming is fun")==['Python']
  assert extract_words("Skywalker")==[]
  assert extract_words("")==[]
output: def extract_words(sentence):
      vowels = "aeiouAEIOU"
      return [word for word in sentence.split() if all(char not in vowels for char in word)]