input: Write a function to detect the vowel in a given string. The function should return the first vowel found in the string. If no vowel is found, the function should 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
      return None
  
  assert vowelCheck("Hello World") == 'e'
  assert vowelCheck("Python") == 'o'
  assert vowelCheck("Fly") == None
  assert vowelCheck("aeiou") == 'a'
  assert vowelCheck("") == None
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
      return None