code: def _check_positional_embeddings(opt):
      """
      Checks positional embedding compatibility with FSDP.
      """
      if not opt.get("learn_positional_embeddings") and should_use_fsdp(
          opt
      ):
          # note: we're doing on-the-fly setting here, abusing pass-by-reference
          # this only works because we're calling this from build_model, which is
          # only done in the original instantiation of an agent.
          opt["learn_positional_embeddings"] = True
          warn_once(
              "Using --ddp_backend zeroX requires --learn-positional-embeddings "
              "true. Forcing this to be true."
          )
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.agents import Agent
  from parlai.utils.torch import padded_3d
  from parlai.core.torch_classifier_agent import TorchClassifierAgent
  from parlai.core.torch_ranker_agent import TorchRankerAgent
  from parlai.core.torch_generator_agent import TorchGeneratorAgent
  from parlai.utils.misc import recursive_getattr, warn_once
  from parlai.utils.logging import logging
  from parlai.utils.fsdp import should_use_fsdp
  from .modules import TransformerMemNetModel, TransformerGeneratorModel, TransformerLinearWrapper
  import torch
label_desc: Use image node_id 1 for calling a global function with example usage: _check_positional_embeddings(opt) without return types