input: def remove_vowels(s: str) -> str:
      """
      Remove all vowels (a, e, i, o, u) from a given string.
  
      >>> remove_vowels("Hello World")
      'Hll Wrld'
      >>> remove_vowels("Python Programming")
      'Pythn Prgrmmng'
      >>> remove_vowels("AI is fun")
      '  s fn'
      """
output:     vowels = "aeiouAEIOU"
      return ''.join([char for char in s if char not in vowels])