code: def load_data_batch(self, data_batch):
          
          if self.sym_gen is not None:
              key = data_batch.bucket_key
              if key not in self.execgrp_bucket:
                  # create new bucket entry
                  symbol = self.sym_gen(key)
                  execgrp = DataParallelExecutorGroup(symbol, self.arg_names,
                                                      self.param_names, self.ctx,
                                                      self.slices, data_batch,
                                                      shared_group=self.execgrp)
                  self.execgrp_bucket[key] = execgrp
  
              self.curr_execgrp = self.execgrp_bucket[key]
          else:
              self.curr_execgrp = self.execgrp
  
          self.curr_execgrp.load_data_batch(data_batch)
docs: Load data and labels into arrays.