input: def create_blockchain_system():
      """ Create a basic blockchain system in Python that includes hash function for the block, 
      a Block class to represent individual blocks, and a Blockchain class to manage the chain.
      The Blockchain class allows adding a new block and getting the chain in JSON format.
      Example:
      >>> from datetime import datetime
      >>> blockchain = Blockchain()
      >>> blockchain.add_block({'timestamp': str(datetime.now()), 'data': 'Block 1'})
      >>> blockchain.add_block({'timestamp': str(datetime.now()), 'data': 'Block 2'})
      >>> blockchain.get_chain()
      '[
        {
          "index": 0,
          "timestamp": "<timestamp>",
          "data": "Block 1",
          "previous_hash": null,
          "hash": "<hash>"
        },
        {
          "index": 1,
          "timestamp": "<timestamp>",
          "data": "Block 2",
          "previous_hash": "<hash>",
          "hash": "<hash>"
        }
      ]'
      """
output:     import hashlib
      import json
      from time import time
  
      class Block:
          def __init__(self, index, timestamp, data, previous_hash):
              self.index = index
              self.timestamp = timestamp
              self.data = data
              self.previous_hash = previous_hash
              self.hash = self.calculate_hash()
  
          def calculate_hash(self):
              block_string = json.dumps(self.__dict__, sort_keys=True).encode()
              return hashlib.sha256(block_string).hexdigest()
  
      class Blockchain:
          def __init__(self):
              self.chain = [self.create_genesis_block()]
  
          def create_genesis_block(self):
              return Block(0, time(), "Genesis Block", "0")
  
          def get_latest_block(self):
              return self.chain[-1]
  
          def add_block(self, data):
              latest_block = self.get_latest_block()
              new_block = Block(latest_block.index + 1, time(), data, latest_block.hash)
              self.chain.append(new_block)
  
          def get_chain(self):
              return json.dumps([block.__dict__ for block in self.chain], indent=2)