class_docstr: Test that we get the right error when the plugin cannot load.
code: def test_tfbam_plugin_does_not_load(self):
      with self.assertRaisesRegexp(
          ImportError,
          "tfbam_lib module not found, cannot read .tfbam files.",
      ):
          _ = sam.SamReader("mouse@25.tfbam")
  
file_path: deepvariant/third_party/nucleus/io/genomics_io_noplugin_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import absltest
  from third_party.nucleus.io import sam
label_desc: Use image node_id 1 for calling the PluginAbsenceTest obj's underlying member method code with example usage: obj.test_tfbam_plugin_does_not_load() without return types