input: Write a python function to create a class that handles JSON-formatted data, with methods to parse JSON data, get data, set new data, and update the JSON string representation.
  assert JSONHandler('{"name": "Alice", "age": 30}').get_data() == {"name": "Alice", "age": 30}
  assert JSONHandler('{"name": "Bob", "age": 25}').get_data() == {"name": "Bob", "age": 25}
  
  json_handler = JSONHandler('{"name": "Charlie", "age": 40}')
  json_handler.set_data({"name": "Charlie", "age": 41})
  assert json_handler.get_data() == {"name": "Charlie", "age": 41}
output: import json
  
  class JSONHandler:
      def __init__(self, json_str):
          self.data = json.loads(json_str)
          
      def parse_json(self, json_str):
          self.data = json.loads(json_str)
          
      def get_data(self):
          return self.data
      
      def set_data(self, new_data):
          self.data = new_data
          self.update_json_string()
          
      def update_json_string(self):
          self.json_str = json.dumps(self.data)