code: def update(self, data, make_backup=True, **kwargs):
          
          from gffutils import create
          from gffutils import iterators
          if make_backup:
              if isinstance(self.dbfn, six.string_types):
                  shutil.copy2(self.dbfn, self.dbfn + '.bak')
  
          # get iterator-specific kwargs
          _iterator_kwargs = {}
          for k, v in kwargs.items():
              if k in constants._iterator_kwargs:
                  _iterator_kwargs[k] = v
  
          # Handle all sorts of input
          data = iterators.DataIterator(data, **_iterator_kwargs)
  
          if self.dialect['fmt'] == 'gtf':
              if 'id_spec' not in kwargs:
                  kwargs['id_spec'] = {
                      'gene': 'gene_id', 'transcript': 'transcript_id'}
              db = create._GTFDBCreator(
                  data=data, dbfn=self.dbfn, dialect=self.dialect, **kwargs)
          elif self.dialect['fmt'] == 'gff3':
              if 'id_spec' not in kwargs:
                  kwargs['id_spec'] = 'ID'
              db = create._GFFDBCreator(
                  data=data, dbfn=self.dbfn, dialect=self.dialect, **kwargs)
  
          else:
              raise ValueError
  
          db._populate_from_lines(data)
          db._update_relations()
          db._finalize()
          return db
docs: Update database with features in `data`.
  
          data : str, iterable, FeatureDB instance
              If FeatureDB, all data will be used. If string, assume it's
              a filename of a GFF or GTF file.  Otherwise, assume it's an
              iterable of Feature objects.  The classes in gffutils.iterators may
              be helpful in this case.
  
          make_backup : bool
              If True, and the database you're about to update is a file on disk,
              makes a copy of the existing database and saves it with a .bak
              extension.
  
          Notes
          -----
          Other kwargs are used in the same way as in gffutils.create_db; see the
          help for that function for details.
  
          Returns
          -------
          FeatureDB with updated features.