input: Write a function to extract the non-vowel words from a given sentence. The function should split the sentence into words and check if each word contains no vowels. If a word contains no vowels, it should be added to the list of non-vowel words. If the sentence is empty, return an empty list.
  assert extract_words("This machine learning project is challenging.")==['This', 'machine', 'learning', 'project', 'is', 'challenging']
  assert extract_words("rt cb bcd")==['rt', 'cb', 'bcd']
  assert extract_words("Hello Python world")==['Python']
  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)]