code: protected void validateSTG(){
  		if(this.stg==null){
  			throw new IllegalArgumentException("stg is null");
  		}
  
  		STGroupValidator stgv = new STGroupValidator(this.stg, MessageRenderer.STG_CHUNKS);
  		if(stgv.getValidationErrors().hasErrors()){
  			throw new IllegalArgumentException(stgv.getValidationErrors().render());
  		}
  	}
docs: Validates the local STGroup
  @throws IllegalArgumentException if the local STGroup was null or not valid