Difficulties using $in with mongodb

I am trying to get all fields present in mongodb. I am using mongoose and I have used $in but when check mongoose log query it is sending wrong parameters

projectkeywordModel.find( { keywordId: { $in: id } } );

but query is passing in monggose like below:-

It works with single Id

projectkeywords.find({ 
  keywordId: { '$in': [ '53bcc3cb7d538efefbe55f98' ] } 
})

but when there is more than one id in array then its not working

 projectkeywords.find({ 
      keywordId: { '$in': [ '53bcc3cb7d538efefbe55f98', '53bcc3bd7d538efefbe55f96' ] } 
    })

here is my Schema

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId=mongoose.Schema.ObjectId;


var ProjectKeyword = new Schema({
  projectId: String,
  keywordId: String,
  developerId: String,


}, {
  versionKey: false,

  toJSON: {
    virtuals: true,
    transform: function(doc, ret, options) {
      ret.id = ret._id.toHexString();
      delete ret._id;
    }
  },

  toObject: {
    virtuals: true
  }
});

module.exports=mongoose.model('ProjectKeyword', ProjectKeyword);