presto-memory-context/src/main/java/io/prestosql/memory/context/AbstractAggregatedMemoryContext.java/AbstractAggregatedMemoryContext/newAggregatedMemoryContext
class AbstractAggregatedMemoryContext:    @Override
    public AbstractAggregatedMemoryContext newAggregatedMemoryContext()
    {
        return new ChildAggregatedMemoryContext(this);
    }