public static <S> UnweightedNode<Void,S> newNodeWithoutAction(UnweightedNode<Void,S> previousNode, S state){
        return new UnweightedNode<Void, S>(previousNode, state, null);
    }
public static < S > UnweightedNode < Void , S > newNodeWithoutAction ( UnweightedNode < Void , S > previousNode , S state ) { return new UnweightedNode < Void , S > ( previousNode , state , null ) ; }
This static method creates an unweighted node without defining an explicit action, using
the parent node and a state.

@param previousNode parent node
@param state state of the node to be created
@param <S> type of the state
@return new node for the state specified, without need of specifying the action connecting them