code: def test_brightness(self) -> None:
      assert round(bcc.RGB(0, 0, 0).brightness, 2) == 0.0
      assert round(bcc.RGB(127, 127, 127).brightness, 2) == 0.5
      assert round(bcc.RGB(128, 128, 128).brightness, 2) == 0.5
      assert round(bcc.RGB(255, 255, 255).brightness, 2) == 1.0
  
imports: from __future__ import annotations
  import pytest
  import bokeh.colors.color
label_desc: Use image node_id 11 for calling the Test_RGB obj's underlying member method code with example usage: obj.test_brightness() without return types