input: Write a function to detect the vowel in a given string. If a vowel is found, return it. If no vowel is found, return an empty string.
  
  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 ''
  
  assert vowelCheck("Hello World")=='e'
  assert vowelCheck("Python")=='o'
  assert vowelCheck("Rhythm")==''
  assert vowelCheck("")==''
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 ''