code: def is_stale(self, assets):
          
          dt = self.datetime
          if self._adjust_minutes:
              adjusted_dt = self._get_current_minute()
          else:
              adjusted_dt = dt
  
          data_portal = self.data_portal
  
          if isinstance(assets, Asset):
              return self._is_stale_for_asset(
                  assets, dt, adjusted_dt, data_portal
              )
          else:
              return pd.Series(data={
                  asset: self._is_stale_for_asset(
                      asset, dt, adjusted_dt, data_portal
                  )
                  for asset in assets
              })
docs: For the given asset or iterable of assets, returns true if the asset
          is alive and there is no trade data for the current simulation time.
  
          If the asset has never traded, returns False.
  
          If the current simulation time is not a valid market time, we use the
          current time to check if the asset is alive, but we use the last
          market minute/day for the trade data check.
  
          Parameters
          ----------
          assets: Asset or iterable of assets
  
          Returns
          -------
          boolean or Series of booleans, indexed by asset.