input: Write a function to create a Python class that modifies the case of a given string. The class should have 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()
  
  assert StringCaseModifier("Hello World").to_upper()=="HELLO WORLD"
  assert StringCaseModifier("Hello World").to_lower()=="hello world"
  assert StringCaseModifier("Hello World").to_title()=="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()