@Override
    public synchronized void init(ProcessingEnvironment env) {

        super.init(env);
        messager = env.getMessager();

        // Populating the supported annotations class.
        annotationsClasses.add(Extension.class);
        annotationsClasses.add(Parameter.class);
        annotationsClasses.add(ParameterOverload.class);
        annotationsClasses.add(ReturnAttribute.class);
        annotationsClasses.add(SystemParameter.class);
        annotationsClasses.add(Example.class);
    }
The annotation processor for siddhi extension annotation validation. This will validate @Extension, @Parameter,
ReturnAttribute, @SystemParameter and @Example annotation and parameters. Note that each of the validation
processor select using the super class where the extension extends or implement.
<p>
annotationsClasses : holds all the supported annotations class.
messager : the messager used to report errors, warnings, and other notices when validation error throws..
modules/siddhi-annotations/src/main/java/io/siddhi/annotation/processor/SiddhiAnnotationProcessor.java