input: def create_blockchain():
      """ Create a simple blockchain system in Python. This function initializes the blockchain with a genesis block, then adds blocks to the chain based on the transactions provided.
      >>> create_blockchain()
      [Block(0, timestamp, 'Genesis Block', '0'), Block(1, timestamp, 'Transaction data', 'hash_of_previous_block')]
      """
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()
  
      blockchain = []
      genesis_block = Block(0, time.time(), 'Genesis Block', '0')
      blockchain.append(genesis_block)
  
      def add_block(data):
          previous_block = blockchain[-1]
          new_block = Block(previous_block.index + 1, time.time(), data, previous_block.hash)
          blockchain.append(new_block)
  
      add_block('Transaction data')
      return blockchain