code: private void insanityCheck(Element element, Meta meta, Opcode.Type type) {
  		if (meta != null) {
  			throw new TemplateException("Invalid operators list on element |%s|. Only one %s operator is allowed.", element, type);
  		}
  	}
docs: Throws template exception if operator of given type is already declared.
  
  @param element context element,
  @param meta operator meta-data,
  @param type operator type.
  @throws TemplateException if operator of given type is already declared.