During the hackathon we talked about aggregators but I have no idea of how they are implemented. For example, Exiobase documents emissions of "HFC"s while we have characterisation factors for different types of HFCs (HFC-41, HFC-152 etc.). This requires some kind of rule to dissagregate HFC emissions into the different subclasses of HFC. How can we implement this kind of aggregation/dissagregation in BONSAI?