     func updateAttribute<In: TensorGroup, Out: TensorGroup>(
         _ name: String, _ value: (In) -> Out) {
         // TODO:
-        assert(false, "Unimplemented [TFFunction] attribute.")
+        fatalError("Unimplemented [TFFunction] attribute.")
     }
 
     func execute() {}

        case .concrete(let h, _):
            return h
        case .symbolic(_, _, _):
            assert(false, "TODO: to be send out in a separate PR.")
            // return op.materialized(index: index)
        }
    }

        case TF_VARIANT: return "variant"
        case TF_UINT32: return "uint32"
        case TF_UINT64: return "uint64"
        default: fatalError("Unhandled type: \(cDataType)")
        }
    }
}
