import click


def format_line_diff(base: str, other: str) -> str:
    """
    Formats the line identifier of a change.

    :param base: The base line number(s).
    :param other: The other line number(s).
    :return: The formatted line numbers.
    """
    buffer = []

    if base:
        buffer.append(f"<{base}")
    if other:
        buffer.append(f">{other}")

    return click.style(f"@@ {' '.join(buffer)} @@", fg='cyan')