public static String nameOf(int id) {
        String name = ID_2_NAME.get(id);
        if (name == null) {
            throw new UnexpectedException("ScopeDefine id = " + id + " not found.");
        }
        return name;
    }
Fetch the name from given id

@param id represents an existing scope id.
@return scope name.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/source/DefaultScopeDefine.java