class_docstr: Optionally wrap inside `context_manager` if condition is `True`.
code: def __init__(self, context_manager, condition):
      self.context_manager = context_manager
      self.condition = condition
  
imports: import functools
  import math
  import numbers
  import random
  import sys
  import timeit
  import warnings
  from collections import defaultdict
  from contextlib import contextmanager
  from itertools import zip_longest
  import numpy
  import torch
  from pyro.poutine.util import site_is_subsample
label_desc: Use image node_id 1 to create a new optional object  with example: obj = optional(context_manager, condition)