presto-main/src/main/java/io/prestosql/metadata/MetadataManager.java/MetadataManager/getAggregateFunctionImplementation
class MetadataManager:    @Override
    public InternalAggregationFunction getAggregateFunctionImplementation(ResolvedFunction resolvedFunction)
    {
        return functions.getAggregateFunctionImplementation(resolvedFunction);
    }