update InterfaceOptions to fix failing test

Author: AlecRosenbaum

graphene/types/interface.py

@@ -5,11 +5,12 @@
 # For static type checking with Mypy
 MYPY = False
 if MYPY:
-    from typing import Dict  # NOQA
+    from typing import Dict, Iterable, Type  # NOQA
 
 
 class InterfaceOptions(BaseOptions):
     fields = None  # type: Dict[str, Field]
+    interfaces = ()  # type: Iterable[Type[Interface]]
 
 
 class Interface(BaseType):
@@ -45,7 +46,7 @@ class Meta:
     """
 
     @classmethod
-    def __init_subclass_with_meta__(cls, _meta=None, **options):
+    def __init_subclass_with_meta__(cls, _meta=None, interfaces=(), **options):
         if not _meta:
             _meta = InterfaceOptions(cls)
 
@@ -58,6 +59,9 @@ def __init_subclass_with_meta__(cls, _meta=None, **options):
         else:
             _meta.fields = fields
 
+        if not _meta.interfaces:
+            _meta.interfaces = interfaces
+
         super(Interface, cls).__init_subclass_with_meta__(_meta=_meta, **options)
 
     @classmethod