input: 
  def remove_vowels(string):
      vowels = ['a','e','i','o','u']
      new_string = ''
      for char in string:
          if char.lower() not in vowels:
              new_string += char
      return new_string
  
  # Example test cases:
  # remove_vowels('Hello World') == 'Hll Wrld'
  # remove_vowels('Python Programming') == 'Pythn Prgrmmng'
  # remove_vowels('aAeEiIoOuU') == ''
  
output:     vowels = ['a','e','i','o','u']
      new_string = ''
      for char in string:
          if char.lower() not in vowels:
              new_string += char
      return new_string