new_contents: from pyexcel_io.sheet import SheetReader
  import pyexcel_io.utils as utils
  from itertools import chain
  
  
  class QuerysetsReader(SheetReader):
  
      def __init__(self, query_sets, column_names, **keywords):
          SheetReader.__init__(self, query_sets, **keywords)
          self.__column_names = column_names
          self.__query_sets = query_sets
  
      def to_array(self):
          """
          Convert query sets into an array
          """
          if len(self.__query_sets) == 0:
              yield []
          for element in SheetReader.to_array(self):
              yield element
  
      def _iterate_rows(self):
          return chain([self.__column_names],
                       self.__query_sets)
  
      def _iterate_columns(self, row):
          if self.__column_names is not None:
              for column in self.__column_names:
                  try:
                      if '__' in column:
                          value = utils._get_complex_attribute(row, column)
                      else:
                          value = utils._get_simple_attribute(row, column)
                      yield value
                  except AttributeError:
                      yield column
  
subject: add missing file