code: def combine_express(samples, combined):
      
      if not combined:
          return None
      to_combine = [dd.get_express_counts(x) for x in
                    dd.sample_data_iterator(samples) if dd.get_express_counts(x)]
      gtf_file = dd.get_gtf_file(samples[0][0])
      isoform_to_gene_file = os.path.join(os.path.dirname(combined), "isoform_to_gene.txt")
      isoform_to_gene_file = express.isoform_to_gene_name(
          gtf_file, isoform_to_gene_file, next(dd.sample_data_iterator(samples)))
      if len(to_combine) > 0:
          eff_counts_combined_file = os.path.splitext(combined)[0] + ".isoform.express_counts"
          eff_counts_combined = count.combine_count_files(to_combine, eff_counts_combined_file, ext=".counts")
          to_combine = [dd.get_express_tpm(x) for x in
                        dd.sample_data_iterator(samples) if dd.get_express_tpm(x)]
          tpm_counts_combined_file = os.path.splitext(combined)[0] + ".isoform.express_tpm"
          tpm_counts_combined = count.combine_count_files(to_combine, tpm_counts_combined_file)
          to_combine = [dd.get_express_fpkm(x) for x in dd.sample_data_iterator(samples)
                        if dd.get_express_fpkm(x)]
          fpkm_counts_combined_file = os.path.splitext(combined)[0] + ".isoform.express_fpkm"
          fpkm_counts_combined = count.combine_count_files(to_combine, fpkm_counts_combined_file, ext=".fpkm")
          return {'counts': eff_counts_combined, 'tpm': tpm_counts_combined,
                  'fpkm': fpkm_counts_combined, 'isoform_to_gene': isoform_to_gene_file}
      return {}
docs: Combine tpm, effective counts and fpkm from express results