public Iterator<Field> getValueIterator(long start, long end) {
		synchronized (dbHandle) {
			return new ValueIterator(start, end);
		}
	}
Get a LongField value iterator over the specified range.
List is pre-calculated such that any changes made to the map
after invoking this method will not be reflected by the iterator
and invalid function keys may be returned.
The implementation assumes a small set of values exist over the 
range.
@param start
@param end
@return Iterator of unique LongField values occuring within the
specified range.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/util/SharedRangeMapDB.java