code: protected boolean isPossibleExtension(JvmFeature feature) {
  		if (!(feature instanceof JvmOperation)) {
  			return false;
  		}
  		List<JvmFormalParameter> parameters = ((JvmExecutable) feature).getParameters();
  		if (parameters.isEmpty()) {
  			return false;
  		}
  		return true;
  	}
docs: Features that are valid extensions are all {@link JvmOperation operations}
  with at least one {@link JvmExecutable#getParameters() parameter}.