How to use the pywaves.crypto.bytes2str function in PyWaves

def burnAsset(self, Asset, quantity, txFee=pywaves.DEFAULT_TX_FEE):
        timestamp = int(time.time() * 1000)

        sData = '\6' + \
                crypto.bytes2str(base58.b58decode(self.publicKey)) + \
                crypto.bytes2str(base58.b58decode(Asset.assetId)) + \
                crypto.bytes2str(struct.pack(">Q", quantity)) + \
                crypto.bytes2str(struct.pack(">Q", txFee)) + \
                crypto.bytes2str(struct.pack(">Q", timestamp))
        signature = crypto.sign(self.privateKey, crypto.str2bytes(sData))
        data = json.dumps({
            "senderPublicKey": self.publicKey,
            "assetId": Asset.assetId,
            "quantity": quantity,
            "timestamp": timestamp,
            "fee": txFee,
            "signature": signature
        })
        req = pywaves.wrapper('/assets/broadcast/burn', data)
        if pywaves.OFFLINE:
            return req
        else:
            return req.get('id', 'ERROR')

txFee = max(txFee, 500000)
            dataObject['fee'] = txFee
            sData = b'\x0c' + \
                    b'\1' + \
                    base58.b58decode(self.publicKey) + \
                    struct.pack(">H", len(data)) + \
                    dataBinary + \
                    struct.pack(">Q", timestamp) + \
                    struct.pack(">Q", txFee)

            dataObject['proofs'] = [ crypto.sign(self.privateKey, sData) ]

            for entry in dataObject['data']:
                if entry['type'] == 'binary':
                    base64Encoded =  base64.b64encode(crypto.str2bytes(entry['value']))
                    entry['value'] = 'base64:' + crypto.bytes2str(base64Encoded)
            dataObjectJSON = json.dumps(dataObject)
            return pywaves.wrapper('/transactions/broadcast', dataObjectJSON)

def burnAsset(self, Asset, quantity, txFee=pywaves.DEFAULT_TX_FEE):
        timestamp = int(time.time() * 1000)

        sData = '\6' + \
                crypto.bytes2str(base58.b58decode(self.publicKey)) + \
                crypto.bytes2str(base58.b58decode(Asset.assetId)) + \
                crypto.bytes2str(struct.pack(">Q", quantity)) + \
                crypto.bytes2str(struct.pack(">Q", txFee)) + \
                crypto.bytes2str(struct.pack(">Q", timestamp))
        signature = crypto.sign(self.privateKey, crypto.str2bytes(sData))
        data = json.dumps({
            "senderPublicKey": self.publicKey,
            "assetId": Asset.assetId,
            "quantity": quantity,
            "timestamp": timestamp,
            "fee": txFee,
            "signature": signature
        })
        req = pywaves.wrapper('/assets/broadcast/burn', data)
        if pywaves.OFFLINE:
            return req