code: def test_darken(self) -> None:
      c = bcc.HSL(10, 0.2, 0.2, 0.2)
      c2 = c.darken(0.1)
      assert c2 is not c
      assert c2.a == 0.2
      assert c2.h == 10
      assert c2.s == 0.2
      assert c2.l == 0.1
  
      c2 = c.darken(0.3)
      assert c2 is not c
      assert c2.a == 0.2
      assert c2.h == 10
      assert c2.s == 0.2
      assert c2.l == 0
  
imports: from __future__ import annotations
  import pytest
  import bokeh.colors.color
label_desc: Use image node_id 2 for calling the Test_Color obj's underlying member method code with example usage: obj.test_darken() without return types