index.js
function (nodes, batchOps, done) {
      self.db.batch(batchOps, function (err) {
        if (err) {
          nodes.forEach(rejectNode)
          return done(err)
        }
        done(null, nodes)
      })
    }
function (nodes, batchOps, done) {
      self.db.batch(batchOps, function (err) {
        if (err) {
          nodes.forEach(rejectNode)
          return done(err)
        }
        done(null, nodes)
      })
    }
function ( nodes , batchOps , done ) { self . db . batch ( batchOps , function ( err ) { if ( err ) { nodes . forEach ( rejectNode ) return done ( err ) } done ( null , nodes ) } ) }
10. perform the leveldb batch op
10 . perform the leveldb batch op