input: def filter_vowels(string):
      vowels = ('a', 'e', 'i', 'o', 'u')
      return ''.join(c for c in string if c not in vowels)
  
  """
  Examples:
  >>> filter_vowels('hello world')
  'hll wrld'
  >>> filter_vowels('python programming')
  'pythn prgrmmng'
  >>> filter_vowels('aeiou')
  ''
  """
output:     vowels = ('a', 'e', 'i', 'o', 'u')
      return ''.join(c for c in string if c not in vowels)