get_haplotypes_pids: Get haplotypes from a vector of pids.
Description
Requires that haplotypes are first populated, e.g.
with pedigrees_all_populate_haplotypes(),
pedigrees_all_populate_haplotypes_custom_founders(), or
pedigrees_all_populate_haplotypes_ladder_bounded().
Usage
get_haplotypes_pids(population, pids)
Value
Matrix of haplotypes where row i is the haplotype of individuals[[i]].