TODO: do we really want to open and close the destination here? Users may want to map quads from multiple input files to one destination.
TODO: do we really want to open and close the destination here? Users may want to map quads from multiple input files to one destination. On the other hand, if the input file doesn't exist, we probably shouldn't open the destination at all, so it's ok that it's happening in this method after checking the input file.
use one of the map functions below
use one of the map functions below
Maps old quads/triples to new quads/triples.