input: Write a function to remove all vowels from a given string.
  assert removeVowels("apple") == "ppl"
  assert removeVowels("banana") == "bnn"
  assert removeVowels("hello world") == "hll wrld"
output: def removeVowels(s):
      vowels = "aeiouAEIOU"
      return ''.join([char for char in s if char not in vowels])