input: 
  def next_block(previous_block, data):
      """Create a new block that follows the given previous block and includes the provided data.
      >>> block = Block(1, '2023-10-01 12:00:00', 'Transaction data', '0')
      >>> next_block(block, 'New transaction data').hash_block()
      '4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b'
      """
      next_index = previous_block.index + 1
      next_timestamp = '2023-10-01 12:00:01'  # Assuming a fixed timestamp for simplicity
      next_data = data
      next_hash = previous_block.hash
      return Block(next_index, next_timestamp, next_data, next_hash)
  
output:     next_index = previous_block.index + 1
      next_timestamp = '2023-10-01 12:00:01'  # Assuming a fixed timestamp for simplicity
      next_data = data
      next_hash = previous_block.hash
      return Block(next_index, next_timestamp, next_data, next_hash)