input: def compose_blockchain():
      """ Composes a basic blockchain system in Python.
      >>> blockchain = compose_blockchain()
      >>> blockchain.add_block({'timestamp': '2023-10-01T12:00:00', 'data': 'Genesis Block'})
      >>> blockchain.add_block({'timestamp': '2023-10-02T12:00:00', 'data': 'Transaction 1'})
      >>> blockchain.get_chain()
      '[
        {
          "index": 0,
          "timestamp": "2023-10-01T12:00:00",
          "data": "Genesis Block",
          "previous_hash": null,
          "hash": "..."  # Omitted for brevity
        },
        {
          "index": 1,
          "timestamp": "2023-10-02T12:00:00",
          "data": "Transaction 1",
          "previous_hash": "...",  # Omitted for brevity
          "hash": "..."  # Omitted for brevity
        }
      ]'
      """
output:     
      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 = f"{self.index}{self.timestamp}{self.data}{self.previous_hash}"
              return hashlib.sha256(block_string.encode()).hexdigest()
  
      class Blockchain:
          def __init__(self):
              self.chain = [self.create_genesis_block()]
  
          def create_genesis_block(self):
              return Block(0, "2023-10-01T12:00:00", "Genesis Block", "0")
  
          def get_latest_block(self):
              return self.chain[-1]
  
          def add_block(self, new_block):
              new_block.index = len(self.chain)
              new_block.previous_hash = self.get_latest_block().hash
              new_block.hash = new_block.calculate_hash()
              self.chain.append(new_block)
  
          def get_chain(self):
              return json.dumps([block.__dict__ for block in self.chain], indent=2)
  
      return Blockchain()
  