input: def create_blockchain():
      """
      Build a simple blockchain system in Python. This function will create a blockchain
      by adding blocks to it, starting from a genesis block. Each block is hashed
      using the SHA-256 algorithm and includes an index, timestamp, data, and the hash
      of the previous block.
      >>> create_blockchain()
      Block: 0, Timestamp: 2023-10-05 12:00:00, Data: Genesis Block, Previous Hash: 0
      Block: 1, Timestamp: 2023-10-05 12:01:00, Data: Transaction 1, Previous Hash: hash1
      Block: 2, Timestamp: 2023-10-05 12:02:00, Data: Transaction 2, Previous Hash: hash2
      """
output:     import hashlib
      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 = f"{self.index}{self.timestamp}{self.data}{self.previous_hash}"
              return hashlib.sha256(block_string.encode()).hexdigest()
  
      blockchain = []
  
      def create_genesis_block():
          return Block(0, "2023-10-05 12:00:00", "Genesis Block", "0")
  
      def next_block(last_block):
          index = last_block.index + 1
          timestamp = time.strftime("%Y-%m-%d %H:%M:%S", time.localtime())
          data = f"Transaction {index}"
          previous_hash = last_block.hash
          return Block(index, timestamp, data, previous_hash)
  
      blockchain.append(create_genesis_block())
  
      for i in range(1, 3):
          blockchain.append(next_block(blockchain[-1]))
  
      for block in blockchain:
          print(f"Block: {block.index}, Timestamp: {block.timestamp}, Data: {block.data}, Previous Hash: {block.previous_hash}")