def get_downbeat_steps(self):
        """
        Return the indices of time steps that contain downbeats.

        Returns
        -------
        downbeat_steps : list
            The indices of time steps that contain downbeats.

        """
        if self.downbeat is None:
            return []
        downbeat_steps = np.nonzero(self.downbeat)[0].tolist()
        return downbeat_steps
Return the indices of time steps that contain downbeats.

        Returns
        -------
        downbeat_steps : list
            The indices of time steps that contain downbeats.