input: def filter_vowels(string: str) -> str:
      """ This function takes a string as input and returns a new string with all vowels removed.
      >>> filter_vowels("hello world")
      "hll wrld"
      >>> filter_vowels("python")
      "pythn"
      """
output:     vowels = "aeiouAEIOU"
      return ''.join([char for char in string if char not in vowels])