docstr: Get the mask from the given state.
docstr_tok: ["Get","the","mask","from","the","given","state","."]
code: def _get_item_mask(self, state: rlt.FeatureData) -> torch.Tensor:
      """Get the mask from the given state."""
      candidate_docs = state.candidate_docs
      assert candidate_docs is not None
      return candidate_docs.mask
  
imports: import enum
  import logging
  from typing import Optional
  import reagent.core.parameters
  import reagent.core.types
  import torch
  import torch.nn.functional
  from reagent.core.dataclasses import field
  from reagent.optimizer import Optimizer__Union, SoftUpdate
  from reagent.training.reagent_lightning_module import ReAgentLightningModule
  from reagent.training.rl_trainer_pytorch import RLTrainerMixin
label_desc: Use image node_id 9 for calling the SlateQTrainer obj's underlying member method code with example usage: obj._get_item_mask(state) and returns: candidate_docs