code: private Integer getHttpStatusCode(ErrorMap error, Shape shape) {
          final Integer httpStatusCode = getHttpStatusCode(error.getErrorTrait());
          return httpStatusCode == null ? getHttpStatusCode(shape.getErrorTrait()) : httpStatusCode;
      }
docs: Get HTTP status code either from error trait on the operation reference or the error trait on the shape.
  
  @param error ErrorMap on operation reference.
  @param shape Error shape.
  @return HTTP status code or null if not present.