creating graph in sublevel

[elf-pavlik]

$ npm install levelup leveldown level-sublevel levelgraph

then running code

var LevelUp = require('levelup'),
    Sublevel = require('level-sublevel'),
    LevelGraph = require('levelgraph');

var db = Sublevel(LevelUp('dev.ldb')),  
    graphdb = LevelGraph(db.sublevel('graph'));

results in

/code/play/levelgraph-sublevel/node_modules/levelgraph/lib/levelgraph.js:75
    , close: leveldb.close.bind(leveldb)
                           ^
TypeError: Cannot call method 'bind' of undefined
    at levelgraph (/code/play/levelgraph-sublevel/node_modules/levelgraph/lib/levelgraph.js:75:28)
    at Object.<anonymous> (/code/play/levelgraph-sublevel/index.js:6:15)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:901:3

[mcollina]

This is fun, I planned to add close to sublevel ;). I think we can just
function wrap close instead of using bind, and let it throw if close is not
there, or silently do nothing. Would you like to assemble a PR for this?

[elf-pavlik]

I don't have much experience with LevelDB... would prefer to focus on few other RDF related issues first and in between follow commits of you and other experienced in this field folks so I can catch up on all the LevelDB arcane techniques 🎒