enum_class_templates,0-based index

I want use my own templement to generate kotin enum class：
{{#gson}}
@SerializedName(value = {{#lambda.doublequote}}{{{@index}}}{{/lambda.doublequote}})
{{/gson}}

I want the SerializedName value to be an increasing string starting from 0。But the @index not work。
In the doc:https://openapi-generator.tech/docs/templating . I find that : If you'd like a 1-based index in your array traversal, you can use {{-index}}。
But what should i do if i want a 0-based index?

Start with the templating documentation and the supplied Kotlin enum template, then generate an enum using the shown @index expression. Compare the generated SerializedName values with the requested sequence; done means the 0-based behavior is clarified or the documented template usage is corrected.