iterate_through is used to calculate the metric at each position
iterate_through(metric, seqc, bp = MulticoreParam(), ...)either `simpson` or `percent`
list of sequences, either passed directly from
process_allele or read_fasta or equivalence
BiocParallel backend. Rule of thumbs: use MulticoreParam(workers = ncpus - 2)
other parameters as needed
return a dataframe containing the position and result.