code: def _init_pool(self):
      if (
          self.check_emb_on_pin_memory()
          and self.pool_size is not None
          and self.buffer_size is not None
          and len(self.histories) > 0
      ):
          self.pool = StreamPool(
              self.pool_size, self.buffer_size, self.hidden_dim
          )
  
file_path: PGL/apps/GNNAutoScale/gnn_models/base_model.py
imports: import os
  import sys
  import numpy
  import paddle
  from pgl.utils.stream_pool import StreamPool, async_write
  from history import History
  from utils import process_batch_data, check_device
label_desc: Use image node_id 2 for calling the ScalableGNN obj's underlying member method code with example usage: obj._init_pool() without return types