code: def save(self, checkpoint):
      if not self.model_built:
          raise RuntimeError(
              "You must call fit_eval or restore first before calling save!"
          )
      state_dict = self.state_dict()
      torch.save(state_dict, checkpoint)
  
imports: import torch
  from torch.utils.data import TensorDataset, DataLoader
  import types
  import numpy
  import math
  import pandas
  import tempfile
  import os
  from zoo.orca.automl.model.abstract import BaseModel, ModelBuilder
  from zoo.orca.automl.metrics import Evaluator
  from zoo.orca.automl.pytorch_utils import LR_NAME, DEFAULT_LR
label_desc: Use image node_id 19 for calling the PytorchBaseModel obj's underlying member method code with example usage: obj.save(checkpoint) without return types