input: def filter_vowels(string: str) -> str:
      """ Filter out all the vowels from a given string.
      >>> filter_vowels("hello world")
      'hll wrld'
      >>> filter_vowels("python is fun")
      'pythn s fn'
      """
output:     vowels = "aeiouAEIOU"
      return ''.join([char for char in string if char not in vowels])