public FcgLevel child(FcgDirection newDirection) {
		if (newDirection == IN_AND_OUT) {
			// undefined--IN_AND_OUT goes in both directions
			throw new IllegalArgumentException("Direction cannot be IN_AND_OUT");
		}

		int newDistance = getDistance() + 1;
		return new FcgLevel(newDistance, newDirection);
	}
Returns the child level of this level.  The child of a level has the same direction 
as this level, with a distance of one more than this level.

@param the direction of the child
@return returns the child 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