improve lod_grid

[WolfgangFahl]

 def update_cell(self, key_value: Any, col_key: str, value: Any) -> None:
        """
        Update a cell in the grid.

        Args:
            key_value (Any): The value of the key column for the row to update.
            row_key (str): The column key of the cell to update.
            value (Any): The new value for the specified cell.

        """
def get_rows_by_key(self) -> Dict[Any, Dict[str, Any]]:
        """
        Organize rows in a dictionary of dictionaries, indexed by the key column value specified in GridConfig.

        Returns:
            Dict[Any, Dict[str, Any]]: A dictionary of dictionaries, with each sub-dictionary representing a row,
                                       indexed by the key column values.
        """