input: 
  def create_blockchain() -> Blockchain:
      """ Create a basic blockchain in Python using only the core modules.
      >>> blockchain = create_blockchain()
      >>> block = blockchain.create_block(nonce=123, previous_hash="0")
      >>> block['block_number'] == 1
      True
      >>> block['nonce'] == 123
      True
      >>> blockchain.hash_block(block)
      'b4ee1fdeb1a242ae66c7960863b6892d2feeeaced0edb81e29c67b9dbf487768'
      """
  
output:     
      class Blockchain:
          def __init__(self):
              self.chain = []
              self.create_block(nonce=1, previous_hash='0')
  
          def create_block(self, nonce: int, previous_hash: str) -> dict:
              block = {
                  'block_number': len(self.chain) + 1,
                  'nonce': nonce,
                  'previous_hash': previous_hash,
                  'timestamp': time.time()
              }
              self.chain.append(block)
              return block
  
          def hash_block(self, block: dict) -> str:
              block_string = json.dumps(block, sort_keys=True).encode()
              return hashlib.sha256(block_string).hexdigest()
  
      return Blockchain()
  