input: from typing import List, Dict
  
  def create_blockchain(blockchain_transactions: List[Dict]) -> List[Block]:
      """
      Create a simple blockchain system in Python. The blockchain is a list of blocks where each block contains an index, a timestamp, data, and the hash of the previous block.
      
      >>> create_blockchain([{'id': 1, 'type': 'transaction'}])
      [<__main__.Block object at 0x7f8b8c0b8d30>]
      """
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):
              sha = hashlib.sha256()
              sha.update(f"{self.index}{self.timestamp}{self.data}{self.previous_hash}".encode('utf-8'))
              return sha.hexdigest()
  
      blockchain = []
      previous_hash = "0"
      for index, transaction in enumerate(blockchain_transactions):
          timestamp = time.time()
          block = Block(index, timestamp, transaction, previous_hash)
          previous_hash = block.hash
          blockchain.append(block)
      
      return blockchain