Enhancement to the currently existing PyType_FromSpec() which creates and returns a heap type from a given spec. PyType_FromSpecWithBases() works similar to PyType_FromSpec(), however it sets the bases of the newly created heap type to the types contained inside the passed bases-tuple.
This allows the programmer to reference other heap-types as base types of  a new heap type. This is necessary as the slot-API, which is used for static declarations of the type-spec, currently relies on statically declared type objects as tp_base or tp_bases entries.