title: Including dict as value in MongoDB mapReduce emit
body: <p>For a map function, I have the following code that works:</p>
  
  <pre><code>self.url_with_sessions_mapper = Code("""
      function(){
          emit(this.page, {'session':this.session, 'time':this.time});
      }
      """)
  </code></pre>
  
  <p>But for some reason, this doesn't:</p>
  
  <pre class="lang-python prettyprint-override"><code>self.url_with_sessions_mapper = Code("""
      function(){
          emit(this.page, {this.session:this.time});
      }
      """)
  </code></pre>
  
  <p>I get this error message</p>
  
  <pre class="lang-none prettyprint-override"><code>on namespace test_database.$cmd failed: exception: SyntaxError: Unexpected token.
  </code></pre>
  
  <p>Why wouldn't the latter syntax work?</p>