input: Write a python function to check if a string starts with a vowel and print an appropriate message.
  assert start_vowel("apple") == "String starts with a vowel"
  assert start_vowel("banana") == "String does not start with a vowel"
  assert start_vowel("umbrella") == "String starts with a vowel"
output: def start_vowel(s):
      vowels = 'aeiouAEIOU'
      if s[0] in vowels:
          return "String starts with a vowel"
      else:
          return "String does not start with a vowel"