def METHOD_NAME(self, token_idxs: List[int]) -> List[int]:
    """Returns frame numbers corresponding to every non-blank token.
    Args:
        token_idxs (List[int]): IDs of decoded tokens.
    Returns:
        List[int]: Frame numbers corresponding to every non-blank token.
    """
    timesteps = []
    for i, token_idx in enumerate(token_idxs):
        if token_idx == self.blank_idx:
            continue
        if i == 0 or token_idx != token_idxs[i - 1]:
            timesteps.append(i)
    return timesteps