premise_region_mapping builds a json containing a regional
mapping to be used by PREMISE. It is written to filename, or
printed to the console if no filename is provided.
Value
Invisibly NULL. Called for its side effect of writing the
json mapping to filename, or of printing it to the console when
filename is NULL.
Examples
# Write the PREMISE topology for the default region mapping
premise_region_mapping(filename = tempfile(fileext = ".json"))
