input: def remove_vowels(string: str) -> str:
      """
      Remove all vowels from a given string.
      >>> remove_vowels('Hello, World!')
      'Hll, Wrld!'
      >>> remove_vowels('Python Programming Language')
      'Pythn Prgrmmng Lngg'
      """
output:     vowels = "aeiouAEIOU"
      return ''.join([char for char in string if char not in vowels])