title: Django rest framework get json instead of count
body: <p>i have a Community app with a field of subscriber related to the accounts app but in the response it return counts instead of using account serializer</p>
  
  <p>CommunitySerializer:</p>
  
  <pre><code>class CommunitySerializer(serializers.ModelSerializer):
  
      class Meta:
          model = Community
          fields = ('name', 'about', 'subscribers', 'moderators')
  </code></pre>
  
  <p>AccountsSerializer:</p>
  
  <pre><code>class UserSerializer(serializers.ModelSerializer):
      class Meta:
          model = User
          fields = ('username',)
  </code></pre>
  
  <p>It Return:</p>
  
  <pre><code>{
  "name": "pcmasterrace",
  "about": "Welcome to the official subreddit of the PC Master Race. In this subreddit, we celebrate and promote the ultimate gaming and working platform. Ascend to a level that respects your eyes, your wallet, your mind, and your heart. Ascend to... the PC Master Race.",
  "community_rules": [
      {
          "rule": "Rule 1 - Off Topic",
          "description": "DOnt fuck"
      },
      {
          "rule": "Rule 2 - No tech support",
          "description": "community_rulescommunity_rulescommunity_rulescommunity_rulescommunity_rules"
      }
  ],
  "subscribers": [
      1
  ],
  "moderators": [
      1
  ]
  }
  </code></pre>