input: from typing import List, Optional
  
  def vowelCheck(inputString: str) -> Optional[str]: 
      """ Detect the first vowel in a given string.
      >>> vowelCheck("Hello World")
      'e'
      >>> vowelCheck("PyThOn")
      'O'
      >>> vowelCheck("Rhythm")
      """
      vowels = ['a','e','i','o','u','A','E','I','O','U'] 
      for x in inputString: 
          if x in vowels: 
              return x
output:     return None