The output nexus file contains the snp data in one of two forms, depending upon what you regard
as most appropriate. One form, that used by Chifman and Kubatko, has two lines per individual,
one providing the reference SNP the second providing the alternate SNP (method=1).
A second form, recommended by Dave Swofford, has
a single line per individual, resolving heterozygous SNPs by replacing them with standard
ambiguity codes (method=2).