input: Write a class to modify the case of a given string. The class should have methods to convert the string to uppercase, lowercase, and title case. If the input string is "Hello World", the output should demonstrate the string in uppercase, lowercase, and title case respectively.
  
  class StringCaseModifier:
      def __init__(self, string):
          self.string = string
  
      def to_upper(self):
          return self.string.upper()
  
      def to_lower(self):
          return self.string.lower()
      
      def to_title(self):
          return self.string.title()
  
  if __name__ == '__main__':
      test_string = 'Hello World'
      string_modifier = StringCaseModifier(test_string)
      print(string_modifier.to_upper())  # Expected: HELLO WORLD
      print(string_modifier.to_lower())  # Expected: hello world
      print(string_modifier.to_title())  # Expected: Hello World
output: class StringCaseModifier:
      def __init__(self, string):
          self.string = string
  
      def to_upper(self):
          return self.string.upper()
  
      def to_lower(self):
          return self.string.lower()
      
      def to_title(self):
          return self.string.title()