code: def scan_file(self, src_file):
          
          self.logger.info('start scanning file {} for proxy list...'
                           .format(src_file))
          with open(src_file, 'r') as fin:
              proxies = json.load(fin)
          for protocol in proxies.keys():
              for proxy in proxies[protocol]:
                  self.proxy_queue.put({
                      'addr': proxy['addr'],
                      'protocol': protocol
                  })
docs: Scan candidate proxies from an existing file