Help to find out why i do have such kind errors when running the program #!usr/bin/python3 import hashlib import json from time import time from uuid import uuid4 from flask import Flask, jsonify, request import requests from urllib.parse import urlparse """ Implementation of blockchain class """ class Blockchain: """ Blockchain class """ def __init__(self): """ default constructor """ self.transactions = [] self.chain = [] self.nodes = set() # store nodes self.block_(previous_hash='1', proof=100) # instantiate a block def validate(self, chain): """ check for valid blocks :param chain: :return: boolean true || false """ last_block = chain[0] index = 1 while index  
 
 
output