public FcgLevel parent() {
		if (direction == IN_AND_OUT) {
			// undefined--we are the parent of all
			throw new IllegalArgumentException(
				"To get the parent of the source level you must use the constructor directly");
		}

		int newDistance = getDistance() - 1;
		FcgDirection newDirection = direction;
		if (newDistance == 0) {
			newDirection = IN_AND_OUT;
		}
		return new FcgLevel(newDistance, newDirection);
	}
Returns the parent level of this level.  The parent of a level has the same direction 
as this level, with a distance of one less than this level.

@return returns the parent level of this level
@throws IllegalArgumentException if this is the source level, which is row 1
Ghidra/Features/GraphFunctionCalls/src/main/java/functioncalls/graph/FcgLevel.java