class_docstr: Parameters
  ----------
  - trading_calendar : catalyst.utils.trading_calendar.TradingCalendar
  - asset_finder : catalyst.assets.AssetFinder
  - readers : dict
      A dict mapping Asset type to the corresponding
      [Minute|Session]BarReader
  - last_available_dt : pd.Timestamp or None, optional
      If not provided, infers it by using the min of the
      last_available_dt values of the underlying readers.
class_docstr_tok: ["Parameters","--","--","--","--","--","-","trading_calendar",":","catalyst.utils.trading_calendar.TradingCalendar","-","asset_finder",":","catalyst.assets.AssetFinder","-","readers",":","dict","A","dict","mapping","Asset","type","to","the","corresponding","[","Minute|Session","]","BarReader","-","last_available_dt",":","pd.Timestamp","or","None",",","optional","If","not","provided",",","infers","it","by","using","the","min","of","the","last_available_dt","values","of","the","underlying","readers","."]
code: def load_raw_arrays(self, fields, start_dt, end_dt, sids):
      asset_types = self._asset_types
      sid_groups = {t: [] for t in asset_types}
      out_pos = {t: [] for t in asset_types}
  
      assets = self._asset_finder.retrieve_all(sids)
  
      for i, asset in enumerate(assets):
          t = type(asset)
          sid_groups[t].append(asset)
          out_pos[t].append(i)
  
      batched_arrays = {
          t: self._readers[t].load_raw_arrays(
              fields, start_dt, end_dt, sid_groups[t]
          )
          for t in asset_types
          if sid_groups[t]
      }
  
      results = []
      shape = self._make_raw_array_shape(start_dt, end_dt, len(sids))
  
      for i, field in enumerate(fields):
          out = self._make_raw_array_out(field, shape)
          for t, arrays in iteritems(batched_arrays):
              out[:, out_pos[t]] = arrays[i]
          results.append(out)
  
      return results
  
imports: from abc import ABCMeta, abstractmethod
  from numpy import full, nan, int64, float64, zeros
  from six import iteritems, with_metaclass
  from catalyst.utils.memoize import lazyval
label_desc: Use image node_id 11 for calling the AssetDispatchBarReader obj's underlying member method code with example usage: obj.load_raw_arrays(fields, start_dt, end_dt, sids) and returns: results