input: Write a function to remove vowels from a given string.
  assert removeVowels("hello world") == "hll wrld"
  assert removeVowels("programming is fun") == "prgrmmng s fn"
  assert removeVowels("aeiou") == ""
output: def removeVowels(s):
      vowels = "aeiouAEIOU"
      return ''.join([char for char in s if char not in vowels])