code: def proxy_num(self, protocol=None):
          
          http_num = len(self.proxies['http'])
          https_num = len(self.proxies['https'])
          if protocol == 'http':
              return http_num
          elif protocol == 'https':
              return https_num
          else:
              return http_num + https_num
docs: Get the number of proxies in the pool
  
          Args:
              protocol (str, optional): 'http' or 'https' or None. (default None)
  
          Returns:
              If protocol is None, return the total number of proxies, otherwise,
              return the number of proxies of corresponding protocol.