title: TypeError: manager_method() argument after ** must be a mapping, not str
body: <p>Sorry, I am new to django rest framework and am having some trouble.</p>
  <p>I am using a nested serializer that I would like to add a create() method for.</p>
  <p>In trying to do so: I have created the following serializers.py:</p>
  <pre><code>class ASerializer(serializers.ModelSerializer):
      class Meta:
          model = A
          fields = (
              &quot;id&quot;,
              &quot;name&quot;,
          )
  
  
  class BSerializer(serializers.ModelSerializer):
      class Meta:
          model = B
          fields = (
              &quot;id&quot;,
              &quot;name&quot;,
          )
  
  
  class CSerializer(serializers.ModelSerializer):
      class Meta:
          model = C
          fields = (
              &quot;id&quot;,
              &quot;name&quot;,
          )
  
  class NSerializer(serializers.ModelSerializer):
      a = ASerializer()
      b = BSerializer()
      c = CSerializer()
  
      class Meta:
          model = N
          fields = (
              &quot;id&quot;,          
              &quot;a&quot;,
              &quot;b&quot;,               
              &quot;c&quot;,
              &quot;description&quot;,
          )
  
      def create(self, validated_data):
          a_data= validated_data.pop(&quot;a&quot;)
          b_data= validated_data.pop(&quot;b&quot;)
          c_data= validated_data.pop(&quot;c&quot;)
          n = N.objects.create(**validated_data)
  
          for one in a.data:
              A.objects.create(n=n, **one)
  
          for two in b.data:
              B.objects.create(n=n, **two)
  
          for three in c.data:
              C.objects.create(n=n, **three)
  
          return n
  </code></pre>
  <p>I want to be able to perform a POST on the data in the following format:</p>
  <pre><code>{
      &quot;id&quot;: 1,
      &quot;a&quot;: {
          &quot;id&quot;: 1,
          &quot;name&quot;: &quot;apple&quot;
      },
      &quot;b&quot;: {
          &quot;id&quot;: 5,
          &quot;name&quot;: &quot;red&quot;
      },
      &quot;c&quot;: {
          &quot;id&quot;: 2,
          &quot;name&quot;: &quot;medium&quot;
      },
      &quot;description&quot;: &quot;a description.&quot;
  }
  </code></pre>
  <p>My models are linked via foreign keys and I can perform requests just fine without the create() in my django admin endpoint (would post my models.py here but the code is already rather large for a question) but I am wondering why I am getting the following error:</p>
  <pre><code>TypeError: django.db.models.manager.BaseManager._get_queryset_methods.&lt;locals&gt;.create_method.&lt;locals&gt;.manager_method() argument after ** must be a mapping, not str
  </code></pre>
  <p>It makes sense that my admin would work fine given that it has no jurisdiction over my serializers from what I understand. I believe this means the error lies here in my serializers.py. Any help would be greatly appreciated, thank you so much!</p>