code: def test_saturate():
      """Test color saturation function"""
      assert saturate("#000", 20) == "#000"
      assert saturate("#fff", 20) == "#fff"
      assert saturate("#8a8", 100) == "#3f3"
      assert saturate("#855", 20) == "#9e3f3f"
  
imports: from __future__ import division
  from pygal.colors import darken, desaturate, hsl_to_rgb, lighten, parse_color, rgb_to_hsl, rotate, saturate, unparse_color
label_desc: Use image node_id 5 for calling a global function with example usage: test_saturate() without return types