Added description to relationships

Author: Sean Dougherty

Diff for: graphene_sqlalchemy/converter.py

@@ -35,7 +35,7 @@ def dynamic_type():
         elif direction in (interfaces.ONETOMANY, interfaces.MANYTOMANY):
             if _type._meta.connection:
                 return createConnectionField(_type._meta.connection)
-            return Field(List(_type))
+            return Field(List(_type), description=getattr(relationship, "doc", None))
 
     return Dynamic(dynamic_type)