@Override
  default String getId() {
    Class<?> clazz = getClass();
    String canonicalName = clazz.getCanonicalName();
    if (canonicalName == null) {
      return clazz.getName();
    }
    return canonicalName;
  }
Return a unique function identifier, used to register the function with {@link
FunctionService}

@return string identifying this function
@since GemFire 6.0
geode-core/src/main/java/org/apache/geode/cache/execute/Function.java