class_docstr: Test the OptsSpec parser works correctly for plot options.
code: def test_plot_opts_nested_brackets(self):
      line = "Curve [title=', '.join(('A', 'B'))]"
      expected = {"Curve": {"plot": Options(title="A, B")}}
      self.assertEqual(OptsSpec.parse(line), expected)
  
imports: from unittest import SkipTest
  from holoviews.element.comparison import ComparisonTestCase
  from holoviews.core.options import Cycle, Options
label_desc: Use image node_id 7 for calling the OptsSpecPlotOptionsTests obj's underlying member method code with example usage: obj.test_plot_opts_nested_brackets() without return types