def annotated_frames_object(scribbles_data, object_id):
    """ Computes which frames have a scribble for a certain object.

    # Arguments
        scribbles_data (dict): Scribble in the default format.
        object_id (int): Id of the object of interest.

    # Returns
        dict: Number of the frames that contain at least one scribble.
    """
    frames_list = []
    scribbles = scribbles_data['scribbles']
    for ii, scribble_frame in enumerate(scribbles):
        for scribble in scribble_frame:
            if scribble['object_id'] == object_id:
                frames_list.append(ii)
                break
    return frames_list
