code: def _get_spot_value(self, assets, field, dt, data_frequency):
      if isinstance(assets, TradingPair):
          spot_values = self.get_exchange_spot_value(
              assets.exchange, [assets], field, dt, data_frequency
          )
  
          if not spot_values:
              return np.nan
  
          return spot_values[0]
  
      else:
          exchange_assets = dict()
          for asset in assets:
              if asset.exchange not in exchange_assets:
                  exchange_assets[asset.exchange] = list()
  
              exchange_assets[asset.exchange].append(asset)
  
          if len(list(exchange_assets.keys())) == 1:
              exchange_name = list(exchange_assets.keys())[0]
              return self.get_exchange_spot_value(
                  exchange_name, assets, field, dt, data_frequency
              )
  
          else:
              spot_values = []
              for exchange_name in exchange_assets:
                  assets = exchange_assets[exchange_name]
                  exchange_spot_values = self.get_exchange_spot_value(
                      exchange_name, assets, field, dt, data_frequency
                  )
                  if len(assets) == 1:
                      spot_values.append(exchange_spot_values)
                  else:
                      spot_values += exchange_spot_values
  
              return spot_values
  
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 5 for calling the DataPortalExchangeBase obj's underlying member method code with example usage: obj._get_spot_value(assets, field, dt, data_frequency) and returns: spot_values, np, self, spot_values