code: def test_alpha():
      assert Color("rgba(0, 0, 0, 1)").alpha == 1
      assert Color("rgba(0, 0, 0, 0)").alpha == 0
      assert 0.49 <= Color("rgba(0, 0, 0, 0.5)").alpha <= 0.51
      c = Color("none")
      c.alpha = 1
      assert c.alpha == 1
  
imports: import ctypes
  import time
  import warnings
  from pytest import mark, raises
  from wand.color import Color
  from wand.compat import xrange
  from wand.version import QUANTUM_DEPTH, MAGICK_VERSION_INFO
label_desc: Use image node_id 10 for calling a global function with example usage: test_alpha() without return types