code: def create_input_peptides_files(
          peptides,
          max_peptides_per_file=None,
          group_by_length=False):
      
      if group_by_length:
          peptide_lengths = {len(p) for p in peptides}
          peptide_groups = {l: [] for l in peptide_lengths}
          for p in peptides:
              peptide_groups[len(p)].append(p)
      else:
          peptide_groups = {"": peptides}
  
      file_names = []
      for key, group in peptide_groups.items():
          n_peptides = len(group)
          if not max_peptides_per_file:
              max_peptides_per_file = n_peptides
          input_file = None
          for i, p in enumerate(group):
              if i % max_peptides_per_file == 0:
                  if input_file is not None:
                      file_names.append(input_file.name)
                      input_file.close()
                  input_file = make_writable_tempfile(
                      prefix_number=i // max_peptides_per_file,
                      prefix_name=key,
                      suffix=".txt")
              input_file.write("%s\n" % p)
          if input_file is not None:
              file_names.append(input_file.name)
              input_file.close()
      return file_names
docs: Creates one or more files containing one peptide per line,
      returns names of files.