input: 
  def filter_vowels(string: str) -> str:
      """ Removes all vowels from the input string and returns the modified 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])