old_contents: from gffutils import example_filename, create, parser, feature
  import gffutils
  import gffutils.biopython_integration as bp
  
  def test_roundtrip():
      """
      Feature -> SeqFeature -> Feature should be invariant.
      """
      db_fname = gffutils.example_filename("gff_example1.gff3")
      db = gffutils.create_db(db_fname, ':memory:')
      feature = db['ENSMUSG00000033845']
      feature.keep_order = True
      dialect = feature.dialect
      s = bp.to_seqfeature(feature)
      f = bp.from_seqfeature(s, dialect=dialect, keep_order=True)
      assert feature == f
  
new_contents: from gffutils import example_filename
  import gffutils
  import gffutils.biopython_integration as bp
  
  def test_roundtrip():
      """
      Feature -> SeqFeature -> Feature should be invariant.
      """
      db_fname = gffutils.example_filename("gff_example1.gff3")
      db = gffutils.create_db(db_fname, ':memory:')
      feature = db['ENSMUSG00000033845']
      feature.keep_order = True
      dialect = feature.dialect
      s = bp.to_seqfeature(feature)
      assert s.location.start.position == feature.start - 1
      assert s.location.end.position == feature.stop
      f = bp.from_seqfeature(s, dialect=dialect, keep_order=True)
      assert feature == f
  
subject: add test for 0- and 1-based indexing