input: Write a python function to remove vowels from a given string.
  assert removeVowels("Hello World") == "Hll Wrld"
  assert removeVowels("Python is fun") == "Pythn s fn"
  assert removeVowels("aeiou") == ""
  assert removeVowels("BCDFG") == "BCDFG"
output: def removeVowels(s):
      vowels = "aeiouAEIOU"
      return ''.join(char for char in s if char not in vowels)