code: def speaker(world):
      utterance = utterance_prior()
      L = literal_listener(utterance)
      pyro.sample("speaker_constraint", L, obs=world)
      return utterance
  
imports: import argparse
  import collections
  import torch
  from search_inference import BestFirstSearch, HashingMarginal, memoize
  import pyro
  import pyro.distributions
label_desc: Use image node_id 15 for calling a global function with example usage: speaker(world) and returns: utterance