input: Write a function to remove all vowels from a given string. The function should return a new string that consists of all the characters from the input string except the vowels. If the input string is empty, the function should return an empty string.
  assert remove_vowels("Hello World")=="Hll Wrld"
  assert remove_vowels("Python Programming")=="Pythn Prgrmmng"
  assert remove_vowels("AEIOUaeiou")==""
  assert remove_vowels("")==""
  assert remove_vowels("This is a test.")=="Ths s  tst."
output: def remove_vowels(s):
      vowels = "AEIOUaeiou"
      return ''.join([char for char in s if char not in vowels])