input: Write a python function to extract and print the vowels from each word in a list of words.
  assert extract_vowels(['hello', 'world']) == ['eo', 'o']
  assert extract_vowels(['apple', 'banana', 'cherry']) == ['ae', 'aaa', 'e']
  assert extract_vowels(['sky', 'fly', 'gym']) == ['', '', '']
output: def extract_vowels(words):
      vowels = "aeiou"
      result = []
      for word in words:
          extracted = ''.join([char for char in word if char in vowels])
          result.append(extracted)
      return result