code: def _get_seqs_from_cluster(seqs, seen):
      
      already_in = set()
      not_in = []
  
      already_in = map(seen.get, seqs)
      # if isinstance(already_in, list):
      already_in = filter(None, already_in)
      not_in = set(seqs) - set(seen.keys())
      # for s in seqs:
      #    if s in seen:
      #        already_in.add(seen[s])
      #    else:
      #        not_in.append(s)
      return list(set(already_in)), list(not_in)
docs: Returns the sequences that are already part of the cluster
  
      :param seqs: list of sequences ids
      :param clus_id: dict of sequences ids that are part of a cluster
  
      :returns:
          * :code:`already_in`list of cluster id that contained some of the sequences
          * :code:`not_in`list of sequences that don't belong to any cluster yet