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// import the necessary modules'use strict';
const mongoose = require('../../lib');const Schema = mongoose.Schema;
// create an export function to encapsulate the model creationmodule.exports = function() {  // define schema  const PersonSchema = new Schema({    name: String,    age: Number,    birthday: Date,    gender: String,    likes: [String],    // define the geospatial field    loc: { type: [Number], index: '2d' }  });
  // define a method to find the closest person  PersonSchema.methods.findClosest = function(cb) {    return mongoose.model('Person').find({      loc: { $nearSphere: this.loc },      name: { $ne: this.name }    }).limit(1).exec(cb);  };
  mongoose.model('Person', PersonSchema);};