code: def _set_final_freeness(self, flag):
          
          if flag:
              self.state.memory.store(self.heap_base + self.heap_size - self._chunk_size_t_size, ~CHUNK_P_MASK)
          else:
              self.state.memory.store(self.heap_base + self.heap_size - self._chunk_size_t_size, CHUNK_P_MASK)
docs: Sets the freedom of the final chunk. Since no proper chunk follows the final chunk, the heap itself manages
          this. Nonetheless, for now it is implemented as if an additional chunk followed the final chunk.