code: def _fill_buffer(self, cnt=None):
      if cnt is None:
          cnt = self._buffer_size - self._buffer_occupancy
      try:
          for _ in range(cnt):
              dp = next(self._iter)
              self._send(dp)
      except StopIteration:
          raise RuntimeError(
              "[{}] buffer_size cannot be larger than the size of the DataFlow when strict=True! "
              "Please use a smaller buffer_size!".format(
                  type(self).__name__
              )
          )
      self._buffer_occupancy += cnt
  
imports: import copy
  import ctypes
  import multiprocessing
  import numpy
  import threading
  import zmq
  from six.moves import queue
  from ..utils.concurrency import StoppableThread, enable_death_signal
  from ..utils.serialize import dumps_once, loads_once
  from .base import DataFlow, DataFlowReentrantGuard, ProxyDataFlow
  from .common import RepeatedData, BatchData
  from .parallel import _bind_guard, _get_pipe_name, _MultiProcessZMQDataFlow, _repeat_iter, _zmq_catch_error
label_desc: Use image node_id 6 for calling the _ParallelMapData obj's underlying member method code with example usage: obj._fill_buffer(cnt) without return types