code: def get_exchange_history_window(
      self,
      exchange_name,
      assets,
      end_dt,
      bar_count,
      frequency,
      field,
      data_frequency,
      ffill=True,
  ):
      pass
  
imports: import abc
  import datetime
  import numpy
  import pandas
  from catalyst.assets._assets import TradingPair
  from catalyst.constants import LOG_LEVEL, AUTO_INGEST
  from catalyst.data.data_portal import DataPortal
  from catalyst.exchange.exchange_bundle import ExchangeBundle
  from catalyst.exchange.exchange_errors import ExchangeRequestError, PricingDataNotLoadedError
  from catalyst.exchange.utils.exchange_utils import resample_history_df, group_assets_by_exchange
  from catalyst.exchange.utils.datetime_utils import get_frequency, get_start_dt
  from logbook import Logger
  from redo import retry
label_desc: Use image node_id 4 for calling the DataPortalExchangeBase obj's underlying member method code with example usage: obj.get_exchange_history_window(exchange_name, assets, end_dt, bar_count, frequency, field, data_frequency, ffill) without return types