code: ProtocolVersion selectProtocolVersion(ProtocolVersion protocolVersion) {
          if (activeProtocols == null) {
              activeProtocols = getActiveProtocols();
          }
  
          return activeProtocols.selectProtocolVersion(protocolVersion);
      }
docs: Select a protocol version from the list. Called from
  ServerHandshaker to negotiate protocol version.
  
  Return the lower of the protocol version suggested in the
  clien hello and the highest supported by the server.