input: 
  def filter_vowels(string: str) -> str:
      """ Filters out all vowels from a given string and returns the resulting string.
      >>> filter_vowels("hello")
      'hll'
      >>> filter_vowels("world")
      'wrld'
      >>> filter_vowels("aeiouAEIOU")
      ''
      >>> filter_vowels("Python")
      'Pythn'
      """
  
output:     vowels = "aeiouAEIOU"
      result = [char for char in string if char not in vowels]
      return ''.join(result)