input: 
  from typing import List
  
  def extract_words(sentence: str) -> List[str]:
      """ Extracts and returns all words in a sentence that contain no vowels.
      >>> extract_words("This machine learning project is challenging.")
      ['machine', 'learning', 'project', 'is', 'challenging']
      >>> extract_words("The quick brown fox jumps over the lazy dog.")
      []
      """
  
output:     vowels = "aeiouAEIOU"
      words = sentence.split()
      result = [word for word in words if all(char not in vowels for char in word)]
      return result