private Optional<String> findModelPropertyAllowableValues(MemberScope<?, ?> member) {
        return Optional.ofNullable(member.getAnnotationConsideringFieldAndGetterIfSupported(ApiModelProperty.class))
                .map(ApiModelProperty::allowableValues)
                .filter(allowableValues -> !allowableValues.isEmpty());
    }
Retrieve the given member's (or its associated getter/field's) {@link ApiModelProperty} annotation and extract its {@code allowableValues}.

@param member targeted field/method
@return {@link ApiModelProperty} annotation's non-empty {@code allowableValues} (or {@code null})
jsonschema-module-swagger-1.5/src/main/java/com/github/victools/jsonschema/module/swagger15/SwaggerModule.java