text: #!/usr/bin/env python3
  
  from utest import *
  from pithy.desc import *
  from pithy.io import outL
  
  # Self-referencing list.
  l_self = []
  l_self.append(l_self)
  
  # Cycle pair.
  l_a = []
  l_b = [l_a]
  l_a.append(l_b)
  
  objs = [
    # These should backref.
    l_self,
    l_a,
    l_b,
  ]
  
  for obj in objs:
    outL()
    outD(repr(obj), obj)
  