code: def fit(
      self, ctx: Context, train_data: DataFrame, validate_data=None
  ):
      if len(ctx.hosts) > 1:
          raise ValueError(
              f"SSHE LinR only support single-host case. Please check configuration."
          )
      if ctx.is_on_host:
          self.init_param["fit_intercept"] = False
      if self.estimator is None:
          single_estimator = SSHELREstimator(
              epochs=self.epochs,
              batch_size=self.batch_size,
              learning_rate=self.learning_rate,
              init_param=self.init_param,
              reveal_every_epoch=self.reveal_every_epoch,
              reveal_loss_freq=self.reveal_loss_freq,
              early_stop=self.early_stop,
              tol=self.tol,
          )
      else:
          logger.info(
              "estimator is not none, will train with warm start"
          )
          single_estimator = self.estimator
          single_estimator.epochs = self.epochs
          single_estimator.batch_size = self.batch_size
      train_data_fit = train_data.copy()
      validate_data_fit = validate_data
      if validate_data:
          validate_data_fit = validate_data.copy()
      single_estimator.fit_single_model(
          ctx, train_data_fit, validate_data_fit
      )
      self.estimator = single_estimator
  
imports: import logging
  import torch
  from fate.arch import Context, dataframe
  from fate.arch.dataframe import DataFrame
  from fate.arch.protocol.mpc.nn.sshe.linr_layer import SSHELinearRegressionLayer, SSHELinearRegressionLossLayer, SSHEOptimizerSGD
  from fate.ml.abc.module import Module, HeteroModule
  from fate.ml.utils import predict_tools
  from fate.ml.utils._convergence import converge_func_factory
  from fate.ml.utils._model_param import get_initialize_func
  from fate.ml.utils._model_param import serialize_param, deserialize_param
label_desc: Use image node_id 4 for calling the SSHELinearRegression obj's underlying member method code with example usage: obj.fit(ctx, train_data, validate_data) without return types