@Override
		public S bound() {
			if (spanTree.isEmpty()) {
				return domain.empty();
			}
			S first = spanTree.firstEntry().getValue().getKey();
			S last = spanTree.lastEntry().getValue().getKey();
			return first.bound(last);
		}
Create a span map on the given domain

<p>
Extensions should invoke this as a super constructor with a fixed domain. See
{@link DefaultULongSpanMap} for an example.

@param domain the domain
Ghidra/Framework/Emulation/src/main/java/generic/Span.java