code: def [](url)
        # normalize the url
        url = URI(url)
  
        # session key
        key = key_for(url)
  
        unless @sessions[key]
          session = Net::HTTP::Proxy(
            @proxy.host,
            @proxy.port,
            @proxy.user,
            @proxy.password
          ).new(url.host,url.port)
  
          session.open_timeout       = @open_timeout       if @open_timeout
          session.read_timeout       = @read_timeout       if @read_timeout
          session.continue_timeout   = @continue_timeout   if @continue_timeout
          session.keep_alive_timeout = @keep_alive_timeout if @keep_alive_timeout
  
          if url.scheme == 'https'
            session.use_ssl     = true
            session.verify_mode = OpenSSL::SSL::VERIFY_NONE
            session.ssl_timeout = @ssl_timeout
            session.start
          end
  
          @sessions[key] = session
        end
  
        return @sessions[key]
      end
docs: Provides an active HTTP session for a given URL.
  
   @param [URI::HTTP, String] url
     The URL which will be requested later.
  
   @return [Net::HTTP]
     The active HTTP session object.