code: def test_darken_rgb(self) -> None:
      c = bcc.RGB(123, 12, 234, 0.2)
      c2 = c.darken(0.1)
      assert c2 is not c
      assert c2.a == 0.2
      assert c2.r == 97
      assert c2.g == 10
      assert c2.b == 185
  
      c2 = c.darken(1.2)
      assert c2 is not c
      assert c2.a == 0.2
      assert c2.r == 0
      assert c2.g == 0
      assert c2.b == 0
  
imports: from __future__ import annotations
  import pytest
  import bokeh.colors.color
label_desc: Use image node_id 3 for calling the Test_Color obj's underlying member method code with example usage: obj.test_darken_rgb() without return types