```
@Target(METHOD)
@Retention(SOURCE)
public static @interface Encoding.IsInit
```
Template method for internal purposes that describes how to ask builder if an attribute was initialized. This must be a boolean-returning no-arg accessor method on a builder. Implementation will always be private regardless if provided method is defined as private or not. If builder encoding is not defined (i.e. no Encoding.Builder), the generator will infer this as a a null check, but if builder encoding is defined with no such IsInit provided, then encoding will be unable to generate code for instantiations of Value.Default or Value.Derived attributes.

Annotation Type Encoding.IsInit