{ CastError: Cast to ObjectId failed for value "" at path "_id" for model "allPublisher"
    at new CastError (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/error/cast.js:27:11)
    at ObjectId.cast (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/schema/objectid.js:158:13)
    at ObjectId.SchemaType._castForQuery (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/schematype.js:1088:15)
    at ObjectId.castForQuery (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/schema/objectid.js:198:15)
    at ObjectId.SchemaType.castForQueryWrapper (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/schematype.js:1045:15)
    at cast (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/cast.js:269:32)
    at model.Query.Query.cast (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/query.js:3302:12)
    at model.Query.Query._castConditions (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/query.js:1292:10)
    at model.Query.Query._findOne (/home/mayur/openRtb/dsp/node_modules/mongoose/lib/query.js:1504:8)
    at /home/mayur/openRtb/dsp/node_modules/kareem/index.js:250:8
    at /home/mayur/openRtb/dsp/node_modules/kareem/index.js:23:7
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)
  message: 'Cast to ObjectId failed for value "" at path "_id" for model "allPublisher"',
  name: 'CastError',
  stringValue: '""',
  kind: 'ObjectId',
  value: '',
  path: '_id',
  reason: undefined,
  model:
   { [Function: model]
     hooks: Kareem { _pres: {}, _posts: {} },
     base:
      Mongoose {
        connections: [Array],
        models: [Object],
        modelSchemas: [Object],
        options: [Object],
        plugins: [Array] },
     modelName: 'allPublisher',
     model: [Function: model],
     db:
      NativeConnection {
        base: [Object],
        collections: [Object],
        models: [Object],
        config: [Object],
        replica: false,
        hosts: null,
        host: 'localhost',
        port: 27017,
        user: undefined,
        pass: undefined,
        name: 'dsp_ux_local',
        options: [Object],
        otherDbs: [],
        states: [Object],
        _readyState: 1,
        _closeCalled: false,
        _hasOpened: true,
        _listening: false,
        db: [Object] },
     discriminators: undefined,
     '$appliedMethods': true,
     '$appliedHooks': true,
     _events: { init: [Function], save: [Function] },
     _eventsCount: 2,
     schema:
      Schema {
        obj: {},
        paths: [Object],
        aliases: {},
        subpaths: {},
        virtuals: [Object],
        singleNestedPaths: {},
        nested: {},
        inherits: {},
        callQueue: [Array],
        _indexes: [],
        methods: {},
        statics: {},
        tree: [Object],
        query: {},
        childSchemas: [],
        plugins: [Array],
        s: [Object],
        _userProvidedOptions: [Object],
        options: [Object],
        '$globalPluginsApplied': true,
        _requiredpaths: [] },
     collection:
      NativeCollection {
        collection: [Object],
        opts: [Object],
        name: 'publisher_inventory',
        collectionName: 'publisher_inventory',
        conn: [Object],
        queue: [],
        buffer: false,
        emitter: [Object] },
     Query: { [Function] base: [Object] },
     '$__insertMany': [Function],
     insertMany: [Function],
     '$init': Promise { [Circular] } } }