code: def seqres_lines(self):
      
    
      lines = []
    
      for chain in self.keys():
        seq = self[chain]
        serNum = 1
        startidx = 0
        while startidx < len(seq):
          endidx = min(startidx+13, len(seq))
          lines += ["SEQRES  %2i %s %4i  %s\n" % (serNum, chain, len(seq), " ".join(seq[startidx:endidx]))]
          serNum += 1
          startidx += 13
      
      return lines
docs: Generate SEQRES lines representing the contents