code: def free_pull(self):
      self._pull_queue.pop(0)
      if len(self._pull_queue) >= self.pool_size:
          pull_data = self._pull_queue[self.pool_size - 1]
          idx, src, index, offset, count = pull_data
          self._async_pull(idx, src, index, offset, count)
      elif len(self._pull_queue) == 0:
          self._pull_index = -1
  
imports: import numpy
  import paddle
  from paddle.framework import core
  from paddle.device import cuda
  from pgl.utils.logger import log
label_desc: Use image node_id 13 for calling the StreamPool obj's underlying member method code with example usage: obj.free_pull() without return types