code: def _query(self, request, filter=None):
          
          limit = None
          offset = None
          if 'maxfeatures' in request.params:
              limit = int(request.params['maxfeatures'])
          if 'limit' in request.params:
              limit = int(request.params['limit'])
          if 'offset' in request.params:
              offset = int(request.params['offset'])
          if filter is None:
              filter = create_filter(request, self.mapped_class, self.geom_attr)
          query = self.Session().query(self.mapped_class)
          if filter is not None:
              query = query.filter(filter)
          order_by = self._get_order_by(request)
          if order_by is not None:
              query = query.order_by(order_by)
          query = query.limit(limit).offset(offset)
          return query.all()
docs: Build a query based on the filter and the request params,
              and send the query to the database.