class_docstr: Parameters
  ---------
  readers : dict[str -> SessionBarReader]
      A dict mapping country codes to SessionBarReader instances to
      service each country.
class_docstr_tok: ["Parameters","--","--","--","--","-","readers",":","dict","[","str","-",">","SessionBarReader","]","A","dict","mapping","country","codes","to","SessionBarReader","instances","to","service","each","country","."]
docstr: Returns the zipline.utils.calendar.trading_calendar used to read
  the data.  Can be None (if the writer didn't specify it).
docstr_tok: ["Returns","the","zipline.utils.calendar.trading_calendar","used","to","read","the","data",".","Can","be","None","(","if","the","writer","did","n't","specify","it",")","."]
code: def trading_calendar(self):
      """
      Returns the zipline.utils.calendar.trading_calendar used to read
      the data.  Can be None (if the writer didn't specify it).
      """
      raise NotImplementedError(
          "HDF5 pricing does not yet support trading calendars."
      )
  
imports: from functools import partial
  import h5py
  import logbook
  import numpy
  import pandas
  from six import iteritems, raise_from, viewkeys
  from six.moves import reduce
  from zipline.data.bar_reader import NoDataAfterDate, NoDataBeforeDate, NoDataForSid, NoDataOnDate
  from zipline.data.session_bars import CurrencyAwareSessionBarReader
  from zipline.utils.memoize import lazyval
  from zipline.utils.numpy_utils import bytes_array_to_native_str_object_array
  from zipline.utils.pandas_utils import check_indexes_all_same
label_desc: Use image node_id 8 for calling the MultiCountryDailyBarReader obj's underlying member method code with example usage: obj.trading_calendar() without return types