new_contents: var mongoose = require('mongoose');
  
  var pollSchema = {
  	title: {
  		type: String,
  		required: true
  	},
  	created_by: {
  		type: mongoose.Schema.Types.ObjectId,
  		required: true,
  		ref: 'User'
  	},
  	choices: [{
  		title: {
  			type: String,
  			required: true
  		},
  		count: {
  			type: Number,
  			required: true
  		}
  	}]
  };
  
  module.exports = new mongoose.Schema(pollSchema);
subject: add poll schema