class_docstr: The general implementation of InternalWindowProcessFunction. The WindowAssigner should be a
  regular assigner without implement PanedWindowAssigner or MergingWindowAssigner.
class_docstr_tok: ["The","general","implementation","of","InternalWindowProcessFunction",".","The","WindowAssigner","should","be","a","regular","assigner","without","implement","PanedWindowAssigner","or","MergingWindowAssigner","."]
code: def prepare_aggregate_accumulator_for_emit(self, window: W):
      acc = self._ctx.get_window_accumulators(window)
      if acc is None:
          acc = self._window_aggregator.create_accumulators()
      self._window_aggregator.set_accumulators(window, acc)
  
imports: from abc import abstractmethod, ABC
  from typing import Generic, List, Iterable, Dict, Set
  from pyflink.common import Row
  from pyflink.common.constants import MAX_LONG_VALUE
  from pyflink.datastream.state import MapState
  from pyflink.fn_execution.table.window_assigner import WindowAssigner, PanedWindowAssigner, MergingWindowAssigner
  from pyflink.fn_execution.table.window_context import Context, K, W
label_desc: Use image node_id 4 for calling the GeneralWindowProcessFunction obj's underlying member method code with example usage: obj.prepare_aggregate_accumulator_for_emit(window) without return types