input: 
  def filter_vowels(string: str) -> str:
      """ Remove all vowels from the given string.
      >>> filter_vowels('hello world')
      'hll wrld'
      >>> filter_vowels('aeiouAEIOU')
      ''
      """
  
output:     vowels = "aeiouAEIOU"
      result = [char for char in string if char not in vowels]
      return ''.join(result)