From section 3.3.2

While this is useful, we might want to return something more human readable such as the IATA
codes for each airport and perhaps the distance property from the edge that tells us how far apart
the airports are. We could add some by modulators to our query to do this.

While one can deduce the meaning of the new term 'modulator' means from the context, it might be helpful to insert here a short definition.