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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def build_payload(self):
        '''
        Builds the payload that will be sent in tracker_request
        '''
        payload = {}
        hashed_info = hashlib.sha1(tparser.bencode(self.torrent_dict['info']))
        self.hash_string = hashed_info.digest()
        self.peer_id = ('-DR' + VERSION +
                        ''.join(random.sample(ALPHANUM, 13)))
        assert len(self.peer_id) == 20
        payload['info_hash'] = self.hash_string
        payload['peer_id'] = self.peer_id
        payload['port'] = self.port
        payload['uploaded'] = 0
        payload['downloaded'] = 0
        payload['left'] = self.length
        payload['compact'] = 1
        payload['supportcrypto'] = 1
        payload['event'] = 'started'
        return payload