input: Write a function to detect the first vowel in a given string. If the string contains vowels, return the first vowel encountered; otherwise, return None.
  def vowelCheck(inputString):
      vowels = ['a','e','i','o','u','A','E','I','O','U']
      for x in inputString:
          if x in vowels:
              return x
  assert vowelCheck("Hello World")=='e'
  assert vowelCheck("Why")==None
  assert vowelCheck("World")=='o'
  assert vowelCheck("")==None
  assert vowelCheck("PYTHON")=='O'
output: def vowelCheck(inputString):
      vowels = ['a','e','i','o','u','A','E','I','O','U']
      for x in inputString:
          if x in vowels:
              return x