input: Write a function to extract the non-vowel words in a given sentence. If the given 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("The quick brown fox jumps over the lazy dog.")==['The', 'quick', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog.']
  assert extract_words("")==[]
output: def extract_words(sentence):
      if not sentence:
          return []
      words = sentence.split()
      return words