docstr: Test ReadAssigner.overlap_len().
docstr_tok: ["Test","ReadAssigner.overlap_len","(",")","."]
code: def test_overlap_len(self, region_1, region_2, expected_overlap):
      """Test ReadAssigner.overlap_len()."""
      self.assertEqual(
          expected_overlap, ranges.overlap_len(region_1, region_2)
      )
      self.assertEqual(
          expected_overlap, ranges.overlap_len(region_2, region_1)
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import itertools
  from absl.testing import absltest
  from absl.testing import parameterized
  import mock
  from third_party.nucleus.protos import position_pb2
  from third_party.nucleus.protos import reference_pb2
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.testing import test_utils
  from third_party.nucleus.util import ranges
label_desc: Use image node_id 35 for calling the RangesTests obj's underlying member method code with example usage: obj.test_overlap_len(region_1, region_2, expected_overlap) without return types