class_docstr: Node in a tree that corresponds to previous interactions with
  a ``ConjectureData`` object according to some fixed test function.
  
  This is functionally a variant patricia trie.
  See https://en.wikipedia.org/wiki/Radix_tree for the general idea,
  but what this means in particular here is that we have a very deep
  but very lightly branching tree and rather than store this as a fully
  recursive structure we flatten prefixes and long branches into
  lists. This significantly compacts the storage requirements.
  
  A single ``TreeNode`` corresponds to a previously seen sequence
  of calls to ``ConjectureData`` which we have never seen branch,
  followed by a ``transition`` which describes what happens next.
code: def forced(self):
      if not self.__forced:
          return EMPTY
      return self.__forced
  
imports: from __future__ import absolute_import, division, print_function
  import attr
  from hypothesis.errors import Flaky, HypothesisException
  from hypothesis.internal.compat import hbytes, int_to_bytes
  from hypothesis.internal.conjecture.data import ConjectureData, DataObserver, Status, StopTest, bits_to_bytes
  from hypothesis.internal.conjecture.junkdrawer import IntList
label_desc: Use image node_id 1 for calling the TreeNode obj's underlying member method code with example usage: obj.forced() and returns: self, EMPTY