input: Write a function to create a simple blockchain system in Python. The function should define a Block class with properties for index, timestamp, data, previous_hash, and hash, and methods to create the hash of the block contents and to create the blockchain. The function should also include methods to create the blockchain and to print the blockchain.
  
  assert create_blockchain() == [create_genesis_block()]
  assert print_blockchain() == None
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()
  
  def create_genesis_block():
      return Block(0, time.time(), "Genesis Block", "0")
  
  def create_blockchain():
      blockchain = [create_genesis_block()]
      return blockchain
  
  def print_blockchain(blockchain):
      for block in blockchain:
          print(f"Index: {block.index}, Timestamp: {block.timestamp}, Data: {block.data}, Previous Hash: {block.previous_hash}, Hash: {block.hash}")