input: Write a function to extract the non-vowel words in a sentence. The function should return a list of words that do not contain any vowels.
  assert extract_words("This machine learning project is challenging.")==["This", "machine", "project", "is", "challenging"]
  assert extract_words("We are working on an important assignment.")==["We", "working", "on", "an", "assignment"]
  assert extract_words("The quick brown fox jumps over the lazy dog.")==["The", "quick", "the", "dog"]
  assert extract_words("Can you see the sky?")==["Cn", "y", "s", "sky"]
  assert extract_words("")==[]
output: def extract_words(sentence):
      vowels = "aeiouAEIOU"
      return [word for word in sentence.split() if not any(char in vowels for char in word)]