    def __determine_subtimesteps_and_nowcast_time_step(self, t, subtimestep_idx):
        """
        Determine the current sub-timesteps and check if the current time step
        requires nowcasting. Updates the `is_nowcast_time_step` flag accordingly.
        """
        if self.__params.time_steps_is_list:
            self.__state.subtimesteps = [
                self.__params.original_timesteps[t_] for t_ in subtimestep_idx
            ]
        else:
            self.__state.subtimesteps = [t]

        if (self.__params.time_steps_is_list and self.__state.subtimesteps) or (
            not self.__params.time_steps_is_list and t > 0
        ):
            self.__state.is_nowcast_time_step = True
        else:
            self.__state.is_nowcast_time_step = False

        if self.__state.is_nowcast_time_step:
            print(
                f"Computing nowcast for time step {t}... ",
                end="",
                flush=True,
            )
Determine the current sub-timesteps and check if the current time step
requires nowcasting. Updates the `is_nowcast_time_step` flag accordingly.
pysteps/blending/steps.py