code: def _get_edge_date(self, date_field, sort):
          '''
          This method is used to get start and end dates for the collection.
          '''
          return self._source.query(self._source_coll, {
                  'q':'*:*',
                  'rows':1,
                  'fq':'+{}:*'.format(date_field),
                  'sort':'{} {}'.format(date_field, sort)}).docs[0][date_fieldf _get_edge_date(self, date_field, sort):
          '''
          This method is used to get start and end dates for the collection.
          '''
          return self._source.query(self._source_coll, {
                  'q':'*:*',
                  'rows':1,
                  'fq':'+{}:*'.format(date_field),
                  'sort':'{} {}'.format(date_field, sort)}).docs[0][date_field]
docs: This method is used to get start and end dates for the collection.