function addApiVersionHeader(endpointRequest) {
	  var api = endpointRequest.service.api;
	  var apiVersion = api.apiVersion;
	  if (apiVersion && !endpointRequest.httpRequest.headers['x-amz-api-version']) {
	    endpointRequest.httpRequest.headers['x-amz-api-version'] = apiVersion;
	  }
	}
add api version header to endpoint operation
@api private