class_docstr: Base class for information retrieval models.
code: def list_available_models(cls) -> Optional[Dict[str, str]]:
      pass
  
imports: import math
  from typing import Dict, Optional
  import numpy
  import torch
  from omegaconf import DictConfig, OmegaConf
  from pytorch_lightning import Trainer
  from nemo.collections.nlp.data import BertInformationRetrievalDataset
  from nemo.collections.nlp.models.nlp_model import NLPModel
  from nemo.collections.nlp.modules.common.lm_utils import get_lm_model
  from nemo.core.classes.common import typecheck
label_desc: Use image node_id 13 for calling the BaseIRModel obj's underlying member method code with example usage: obj.list_available_models(cls) without return types