title: AssertionError: Found different types with the same name in the schema
body: <p>I have two classes: Products and SalableProducts in my models (SalableProducts inherits from Products so it has every field of it's database). Here is my schema down below</p>
  
  <p>I tried including the "exclude_fields" property but that didn't work</p>
  
  <p><b>Product_schema.py:</b></p>
  
  <pre class="lang-py prettyprint-override"><code>class Product(SQLAlchemyObjectType):
   class Meta:
    model = ProductModel
    interfaces = (relay.Node, )
  
  class ProductConnections(relay.Connection):
   class Meta:
    node = Product
  </code></pre>
  
  <p><b>Salable_product_schema.py:</b></p>
  
  <pre class="lang-py prettyprint-override"><code>class SalableProduct(SQLAlchemyObjectType):
   class Meta:
    model = SalableProductModel
    interfaces = (relay.Node, )
  
  class SalableProductConnections(relay.Connection):
   class Meta:
    node = SalableProduct
  
  </code></pre>
  
  <p><b>Schema.py:</b></p>
  
  <pre class="lang-py prettyprint-override"><code>class Query(graphene.ObjectType):
   node = relay.Node.Field()
   all_products = SQLAlchemyConnectionField(ProductConnections)
   all_salable_products = 
    SQLAlchemyConnectionField(SalableProductConnections)
  </code></pre>
  
  <p>The result is this error : </p>
  
  <blockquote>
    <p>AssertionError: Found different types with the same name in the schema: product_status, product_status.</p>
  </blockquote>
  
  <p>(product_status is a propery shared by the two classes by inheritance)</p>