def cleanupBox(box):
    """Return a sparse copy of `box`, without redundant (default) values.

        >>> cleanupBox({})
        {}
        >>> cleanupBox({'wdth': (0.0, 1.0)})
        {'wdth': (0.0, 1.0)}
        >>> cleanupBox({'wdth': (-1.0, 1.0)})
        {}

    """
    return {tag: limit for tag, limit in box.items() if limit != (-1.0, 1.0)}