code: def write_diversity_metrics(data, sample_ids, fp=None):
      
      if fp is None:
          fp = "./diversity_data.txt"
  
      with open(fp, "w") as outf:
          out = csv.writer(outf, delimiter="\t")
          out.writerow(["SampleID", "Group", "Calculation"])
          for group, d in data.iteritems():
              for sid, value in d.iteritems():
                  out.writerow([sid, group, value])
docs: Given a dictionary of diversity calculations (keyed by method)
      write out the data to a file.