input: from typing import List, Optional
  
  def vowelCheck(inputString: str) -> Optional[str]:
      """
      Detects the first vowel in a given string and returns it. If no vowel is found, returns None.
      >>> vowelCheck("Hello World")
      'e'
      >>> vowelCheck("Brrr")
      
      """
      vowels = ['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']
      for x in inputString:
          if x in vowels:
              return x
output:     return None