_ad_init_object fix

Author: jrmaddison

firedrake/adjoint_utils/function.py

@@ -342,9 +342,10 @@ class CofunctionMixin(FunctionMixin):
     def _ad_dot(self, other):
         return firedrake.assemble(firedrake.action(self, other))
 
+    @classmethod
     def _ad_init_object(cls, obj):
         from firedrake import Cofunction
-        return Cofunction(cls.function_space()).assign(obj)
+        return Cofunction(obj.function_space()).assign(obj)
 
     def _ad_init_zero(self, dual=False):
         from firedrake import Function, Cofunction