new_contents: import unittest
  
  from ..channel2 import Channel
  
  from intervaltree import Interval
  
  
  class ChannelTests(unittest.TestCase):
      def setUp(self):
          tracks = [(1, 2, 0), (1, 3, 1), (3, 5, 2)]
          self.channel = Channel(tracks)
  
      def test_init(self):
          self.assertEqual(
              self.channel.tracks, [(1, 2, 0), (1, 3, 1), (3, 5, 2)]
          )
  
      def test_pack(self):
          self.channel.pack_tracks()
          self.assertEqual(len(self.channel.trees), 2)
  
          self.assertEqual(
              [xx for xx in self.channel.trees[0]],
              [Interval(1, 3, 0), Interval(3, 6, 2)]
          )
          self.assertEqual(
              [xx for xx in self.channel.trees[1]], [Interval(1, 4, 1)]
          )
  
subject: add channel2 test