title: Django Graphene, Passing JSON or dict data as input for Mutation
body: <p>I have the following situation: I have a User, each user has a Inventory. I'm struggling to declare the user's inventory in the Mutation "CreateUser". Here is the following mutation for creating the user:</p>
  
  <pre><code>mutation Create{
    addUser(UserData:{name:"Shibunika",age:21}
  }
  </code></pre>
  
  <p>I'm trying to declare the user's inventory in this mutation, I expected something like</p>
  
  <pre><code>mutation Create{
    addUser(UserData:{name:"Shibunika",age:21,inventory:{'item1':45,'item2':25}
  }s
  </code></pre>
  
  <p>these number are the quantity of each item.
  How do I define these inputs in graphene?
  Would you gently show me a schema for this?</p>