code: function hasCustomEndpoint(client) {
    //if set endpoint is set for specific client, enable endpoint discovery will raise an error.
    if (client._originalConfig && client._originalConfig.endpoint && client._originalConfig.endpointDiscoveryEnabled === true) {
      throw util.error(new Error(), {
        code: 'ConfigurationException',
        message: 'Custom endpoint is supplied; endpointDiscoveryEnabled must not be true.'
      });
    };
    var svcConfig = AWS.config[client.serviceIdentifier] || {};
    return Boolean(AWS.config.endpoint || svcConfig.endpoint || (client._originalConfig && client._originalConfig.endpoint));
  }
docs: If endpoint is explicitly configured, SDK should not do endpoint discovery in anytime.
  @param [object] client Service client object.
  @api private