DynaSOAr is a dynamic object allocator for GPGPU that enables object-oriented programming with an efficient structure-of-arrays (SOA) memory layout. One of the limitations in DynaSOAr is its poor support for nested objects. When a class has a field of another class, the fields of the inner class are allocated in an arrays-of-structure layout. This paper proposes a technique that translates nested class definitions into flat ones by inlining inner classes into top-level classes. We implemented this technique as a Sanajeh domain-specific language that translates Python class definitions into C++ classes using DynaSOAr. Our preliminary evaluation showed that Sanajeh executes a parallel benchmark program with nested objects at almost the same speed as the one with manually flatten classes.