static boolean isAnnotatedNullable(AnnotatedElement annotatedElement) {
        for (Annotation a : annotatedElement.getAnnotations()) {
            final String annotationTypeName = a.annotationType().getName();
            if (annotationTypeName.endsWith(".Nullable")) {
                return true;
            }
        }
        return false;
    }
Returns an attribute resolver which retrieves a value specified by {@code attrKeys}
from the {@link RequestContext}.
core/src/main/java/com/linecorp/armeria/internal/server/annotation/AnnotatedValueResolver.java