              <object pk="1"></object>
          </field>
      </object>
      <object pk="1" model="serializers.author">
          <field type="CharField" name="name">Agnes</field>
      </object>
 
</s> remove     ]
 </s> add     ],
    "meta_data": []
        <field to="serializers.categorymetadata" name="meta_data" rel="ManyToManyRel"></field>
              <object pk="1"></object>
          </field>
        <field to="serializers.categorymetadata" name="meta_data" rel="ManyToManyRel"></field>
      </object>
      <object pk="1" model="serializers.author">
          <field type="CharField" name="name">Agnes</field>
      </object>
keep add keep keep keep keep
 Fixed #19820 -- Added more helpful error messages to Python deserializer. 
tests/serializers/tests.py