def _is_name_start(css, pos):
    """Return true if the given character is a name-start code point."""
    # https://www.w3.org/TR/css-syntax-3/#name-start-code-point
    c = css[pos]
    return (
        c in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_' or
        ord(c) > 0x7F)