input: 
  def extract_words(sentence: str) -> List[str]:
      """ Extracts and returns a list of words in the sentence that do not contain any vowels.
      >>> extract_words("This machine learning project is challenging.")
      ['machine', 'learning', 'project', 'is', 'challenging']
      """
      non_vowel_words = []
      words = sentence.split()
      vowels = ['a','e','i','o','u','A','E','I','O','U']
      for word in words:
          if not any(char in vowels for char in word):
              non_vowel_words.append(word) 
      return non_vowel_words
  
output:     return words