code: def add_window(self, new_window: W, merge_function: MergeFunction[W]):
      windows = []
      windows.extend(self._mapping.keys())
      windows.append(new_window)
  
      merge_results = dict()
      self._window_assigner.merge_windows(
          windows, MergeResultsCallback(merge_results)
      )
  
      result_window = new_window
      merged_new_window = False
  
      for merge_result, merged_windows in merge_results.items():
          if new_window in merged_windows:
              merged_new_window = True
              merged_windows.remove(new_window)
              result_window = merge_result
  
          merged_state_window = self._mapping[
              next(iter(merged_windows))
          ]
  
          merged_state_windows = []
          for merged_window in merged_windows:
              if merged_window in self._mapping:
                  res = self._mapping.pop(merged_window)
                  merged_state_windows.append(res)
  
          self._mapping[merge_result] = merged_state_window
          merged_state_windows.remove(merged_state_window)
  
          if (
              merge_result not in merged_windows
              or len(merged_windows) != 1
          ):
              merge_function.merge(
                  merge_result,
                  merged_windows,
                  self._mapping[merge_result],
                  merged_state_windows,
              )
  
      if len(merge_results) == 0 or (
          result_window == new_window and not merged_new_window
      ):
          self._mapping[result_window] = result_window
  
      return result_window
  
file_path: flink/flink-python/pyflink/fn_execution/datastream/window/merging_window_set.py
imports: from abc import ABC, abstractmethod
  from typing import TypeVar, Generic, Collection, Iterable
  from pyflink.datastream import MergingWindowAssigner
  from pyflink.datastream.state import MapState
label_desc: Use image node_id 5 for calling the MergingWindowSet obj's underlying member method code with example usage: obj.add_window(new_window, merge_function) and returns: result_window