input: 
  def filter_vowels(string):
      """Filters out all the vowels from a given string.
      >>> filter_vowels("hello")
      'hll'
      >>> filter_vowels("AEIOUaeiou")
      ''
      """
      vowels = ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U')
      return ''.join(c for c in string if c not in vowels)
  
output:     vowels = ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U')
      return ''.join(c for c in string if c not in vowels)