input: def filter_vowels(string: str) -> str:
      """ Filter out all the vowels from a given string.
      >>> filter_vowels('hello')
      'hll'
      >>> filter_vowels('world')
      'wrld'
      >>> filter_vowels('aeiou')
      ''
      """
      vowels = ('a', 'e', 'i', 'o', 'u')
      return ''.join(c for c in string if c not in vowels)
output:     vowels = ('a', 'e', 'i', 'o', 'u')
      return ''.join(c for c in string if c not in vowels)