code: function appendModel(url, model, done){
  		var list = utils.flatten_tree(JSON.parse(JSON.stringify(model)))
  
  		var errormodel = null
  
  		list = list.filter(function(model){
  			if(!model._digger.path || !model._digger.inode){
  				errormodel = model;
  				return false;
  			}
  			return true
  		})
  
  		if(errormodel){
  			return done('no path or inode in level-append: ' + JSON.stringify(model))
  		}
  
  		var batch = list.map(function(model){
  			return {
  				type:'put',
  				key:model._digger.path + '/' + model._digger.inode,
  				value:model
  			}
  		})
  
  		tree.batch(batch, function(err){
  			if(err) return done(err)
  			done(null, model)
  		})
  	}
docs: append a single model