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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 generate_payload(self, command, data=None):
 """ Generate the payload to send. Args: command(str):
 The type of command. This is one of the entries from payload_dict data(dict, optional):
 The data to be send. This is what will be passed via the 'dps' entry """

        json_data = payload_dict[self.dev_type][command]['command']

        if 'gwId' in json_data:
            json_data['gwId'] = self.id
        if 'devId' in json_data:
            json_data['devId'] = self.id
        if 'uid' in json_data:
            json_data['uid'] = self.id  # still use id, no seperate uid
        if 't' in json_data:
            json_data['t'] = str(int(time.time()))

        if data is not None:
            json_data['dps'] = data

        # Create byte buffer from hex data
        json_payload = json.dumps(json_data)
        #print(json_payload)
        json_payload = json_payload.replace(' ', '')  # if spaces are not removed device does not respond!
        json_payload = json_payload.encode('utf-8')
        log.debug('json_payload=%r', json_payload)

        if command == SET:
            # need to encrypt
            #print('json_payload %r' % json_payload)
            self.cipher = AESCipher(self.local_key)  # expect to connect and then disconnect to set new
            json_payload = self.cipher.encrypt(json_payload)
            #print('crypted json_payload %r' % json_payload)
            preMd5String = b'data=' + json_payload + b'||lpv=' + PROTOCOL_VERSION_BYTES + b'||' + self.local_key
            #print('preMd5String %r' % preMd5String)
            m = md5()
            m.update(preMd5String)
            #print(repr(m.digest()))
            hexdigest = m.hexdigest()
            #print(hexdigest)
            #print(hexdigest[8:][:16])
            json_payload = PROTOCOL_VERSION_BYTES + hexdigest[8:][:16].encode('latin1') + json_payload
            #print('data_to_send')
            #print(json_payload)
            #print('crypted json_payload (%d) %r' % (len(json_payload), json_payload))
            #print('json_payload  %r' % repr(json_payload))
            #print('json_payload len %r' % len(json_payload))
            #print(bin2hex(json_payload))
            self.cipher = None  # expect to connect and then disconnect to set new


        postfix_payload = hex2bin(bin2hex(json_payload) + payload_dict[self.dev_type]['suffix'])
        #print('postfix_payload %r' % postfix_payload)
        #print('postfix_payload %r' % len(postfix_payload))
        #print('postfix_payload %x' % len(postfix_payload))
        #print('postfix_payload %r' % hex(len(postfix_payload)))
        assert len(postfix_payload) <= 0xff
        postfix_payload_hex_len = '%x' % len(postfix_payload)  # TODO this assumes a single byte 0-255 (0x00-0xff)
        buffer = hex2bin( payload_dict[self.dev_type]['prefix'] + 
                          payload_dict[self.dev_type][command]['hexByte'] + 
                          '000000' +
                          postfix_payload_hex_len ) + postfix_payload
        #print('command', command)
        #print('prefix')
        #print(payload_dict[self.dev_type][command]['prefix'])
        #print(repr(buffer))
        #print(bin2hex(buffer, pretty=True))
        #print(bin2hex(buffer, pretty=False))
        #print('full buffer(%d) %r' % (len(buffer), buffer))
        return buffer