code: def set_features(self):
          Merge all psms and peptides"""
          allpsms_str = readers.generate_psms_multiple_fractions_strings(
              self.mergefiles, self.ns)
          allpeps = preparation.merge_peptides(self.mergefiles, self.ns)
          self.features = {'psm': allpsms_str, 'peptide': allpeps}
docs: Merge all psms and peptides