The Interval class implements a Region which represents upper
and/or lower limits on one or more axes of a Frame. For a point to
be within the region represented by the Interval, the point must
satisfy all the restrictions placed on all the axes. The point is
outside the region if it fails to satisfy any one of the restrictions.
Each axis may have either an upper limit, a lower limit, both or
neither. If both limits are supplied but are in reverse order (so
that the lower limit is greater than the upper limit), then the
interval is an excluded interval, rather than an included interval.
Note, The Interval class makes no allowances for cyclic nature of
some coordinate systems (such as SkyFrame coordinates). A Box
should usually be used in these cases since this requires the user
to think about suitable upper and lower limits,