docs: def aggregate(self, query: Optional[dict] = None,
                    group: Optional[dict] = None,
                    order_by: Optional[tuple] = None) -> List[IModel]:
          """Get aggregated results
  
          : param query: Rulez based query
          : param group: Grouping structure
          : param order_by: Tuple of ``(field, order)`` where ``order`` is
                           ``'asc'`` or ``'desc'``
  
          : todo: Grouping structure need to be documented
  
          """
          raise NotImplementedError