code: def add_seqs_to_alignment(seqs_fp, aln_fp, moltype=DNA,
                            params=None, accurate=False):
      
      if params is None:
          params = {'--seed': aln_fp}
      else:
          params['--seed'] = aln_fp
  
      return align_unaligned_seqs(seqs_fp, moltype, params, accurate)
docs: Returns an Alignment object from seqs and existing Alignment.
  
      The "--seed" option can be used for adding unaligned sequences into
      a highly reliable alignment (seed) consisting of a small number of
      sequences.
  
      Parameters
      ----------
      seqs_fp : string
          file path of the unaligned sequences
      aln_fp : string
          file path of the seed alignment
      params : dict of parameters to pass in to the Mafft app controller.
  
      Returns
      -------
          The aligned sequences. The seq in the seed alignment will have
          "_seed_" prefixed to their seq id.