def _info_from_first_line(line):
    """
    Gets the info from the first line of landmarks' txt. The format of the file
    is hardcoded for now, e.g. the expected numbers and fields.
    It returns a dictionary, which enables future extensions of what is returned.

    Along with the functions _from_line_to_vec, from_txt_to_numpy_points, and
    access_ln_frame they are the functions to access the single txt (with sparse
    landmarks) per video.
    Unless you know how to call the function, please avoid calling it directly, it is used
    internally by the from_txt_to_numpy_points().
    :param line:
    :return: Dict with meta-data.
    """
    info = {}
    # # get the framename of the first (assumed int!)
    info['init_framename'] = int(line[line.find(':') + 1: line.find('\t')])
    # # get the number of frames.
    line1 = line[line.find('n_frames:'):]
    info['n_frames'] = int(line1[9: line1.find('\t')])
    # # get the number of landmarks.
    line2 = line[line.find('n_landmarks:'):]
    info['n_landm'] = int(line2[12: line2.find('\n')])
    return info