docs: def build_opener(self):
          """
          Builds url opener, initializing proxy.
          @return: OpenerDirector
          """
          http_handler = urllib2.HTTPHandler() # debuglevel=self.transport.debug
  
          if util.empty(self.transport.proxy_url):
              return urllib2.build_opener(http_handler)
  
          proxy_handler = urllib2.ProxyHandler(
              {self.transport.proxy_url[:4]: self.transport.proxy_url})
  
          return urllib2.build_opener(http_handler, proxy_handler)