def summarize_id(id):
    """
    Docker uses hexadecimal strings of 65 characters to uniquely identify
    containers, images and other objects. Docker's API almost always reports
    full IDs of 65 characters, but the ``docker`` program abbreviates these IDs
    to 12 characters in the user interface. We do the same because it makes the
    output more user friendly.

    :param id: A hexadecimal ID of 65 characters.
    :returns: A summarized ID of 12 characters.
    """
    return id[:12]