@Override
		public Field previous() throws IOException {
			if (hasPrev || hasPrevious()) {
				hasNext = true;
				hasPrev = false;
				lastKey = indexKey;
				return indexKey.getIndexedField();
			}
			return null;
		}
Construct an index field iterator.  The iterator is positioned at index
value identified by startValue.
@param minValue minimum index value or null if no minimum
@param maxValue maximum index value or null if no maximum
@param startValue initial index value position
@param before if true initial position is before minValue, else position
after maxValue
@throws IOException an IO error occurred
Ghidra/Framework/DB/src/main/java/db/FieldIndexTable.java