text: from pymc3.memoize import memoize
  
  def getmemo():
      @memoize
      def f(a, b=['a']):
          return str(a) + str(b)
      return f
  
  
  def test_memo():
      f = getmemo()
  
      assert f('x', ['y', 'z']) == "x['y', 'z']"
      assert f('x', ['a', 'z']) == "x['a', 'z']"
      assert f('x', ['y', 'z']) == "x['y', 'z']"
  