input: Write a python function to remove all vowels from a given string.
  assert remove_vowels("Hello World") == "Hll Wrld"
  assert remove_vowels("Python Programming") == "Pythn Prgrmmng"
  assert remove_vowels("Beautiful Day") == "Btfl Dy"
output: def remove_vowels(s):
      vowels = "aeiouAEIOU"
      return ''.join(char for char in s if char not in vowels)