input: Write a Python class to modify the case of the string. The class should include methods to convert the string to uppercase, lowercase, and title case.
  
  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()
  
  # Testing the class with the given input
  test_string = 'Hello World'
  string_modifier = StringCaseModifier(test_string)
  assert string_modifier.to_upper() == 'HELLO WORLD'
  assert string_modifier.to_lower() == 'hello world'
  assert string_modifier.to_title() == 'Hello World'
output: 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()