A set of loci on a contig, stored/manipulated as loci ranges.
An immutable collection of genomic regions on any number of contigs.
Used, for example, to keep track of what loci to call variants at.
Since contiguous genomic intervals are a common case, this is implemented with sets of (start, end) intervals.
All intervals are half open: inclusive on start, exclusive on end.
A map from contig-name to Contig, which is a set or genomic intervals as described above.