Returns dotted-decimal reperesentation

def dotted(self):
        " Returns dotted-decimal reperesentation "
        obj = libcrypto.OBJ_nid2obj(self.nid)
        buf = create_string_buffer(256)
        libcrypto.OBJ_obj2txt(buf, 256, obj, 1)
        if pyver == 2:
            return buf.value
        else:
            return buf.value.decode('ascii')