docstr: Attempts to offload the region and prefetch it in backward pass.
docstr_tok: ["Attempts","to","offload","the","region","and","prefetch","it","in","backward","pass","."]
code: def _try_to_offload(
      self, host_region: Region, offload_region: Region
  ):
      """
      Attempts to offload the region and prefetch it in backward pass.
      """
  
      # record previous information
      orig_prefetch = host_region.bwd_prefetch_region
      orig_is_syn = offload_region.is_syn
      orig_need_offload = offload_region.need_offload
  
      if host_region == offload_region:
          offload_region.is_syn = True
      else:
          host_region.bwd_prefetch_region = offload_region
      offload_region.need_offload = True
  
      ts, profit = self._eval_one_choice()
  
      # restore previous information
      host_region.bwd_prefetch_region = orig_prefetch
      offload_region.is_syn = orig_is_syn
      offload_region.need_offload = orig_need_offload
  
      return ts, profit
  
imports: import time
  from abc import ABC, abstractmethod
  from typing import Dict, List, Type
  import torch
  from torch.fx.node import Node
  from colossalai.utils.device import get_current_device
  from .region import Region
  from .training_simulator import AsynTrainingSimulator, SynTrainingSimulator, TrainingSimulator
  from .util import NodeInfo, NvDevicePower
label_desc: Use image node_id 4 for calling the AsynGreedySolver obj's underlying member method code with example usage: obj._try_to_offload(host_region, offload_region) and returns: ts,  profit