input: from typing import List
  
  def print_blockchain(blockchain: List[Block]) -> None:
      """ Prints the blockchain by iterating through each block
      and displaying the block's index, timestamp, data, and hash.
      """
      for block in blockchain:
          block_index = str(block.index)
          block_timestamp = str(block.timestamp)
          block_data = str(block.data)
          block_hash = block.hash
          print(f"Index: {block_index}, Timestamp: {block_timestamp}, Data: {block_data}, Hash: {block_hash}")
  
  # Example usage:
  # blockchain_to_print = create_blockchain()
  # print_blockchain(blockchain_to_print)
  # Output:
  # Index: 0, Timestamp: whatever_timestamp, Data: Genesis Block, Hash: whatever_hash
  # Index: 1, Timestamp: another_timestamp, Data: another_data, Hash: another_hash
  # and so on for each block in the blockchain...
output:     for block in blockchain:
          block_index = str(block.index)
          block_timestamp = str(block.timestamp)
          block_data = str(block.data)
          block_hash = block.hash
          print(f"Index: {block_index}, Timestamp: {block_timestamp}, Data: {block_data}, Hash: {block_hash}")