Destroy the multiprocessing environment and its slave environments.

def destroy(self, folder=None, as_coro=False):
        """Destroy the multiprocessing environment and its slave environments.
        """
        async def _destroy(folder):
            ret = self.save_info(folder)
            await self.stop_slaves()
            # Terminate and join the process pool when we are destroyed.
            # Do not wait for unfinished processed with pool.close(),
            # the slaves should be anyway already stopped.
            if self._pool is not None:
                self._pool.terminate()
                self._pool.join()
            await self._env.shutdown(as_coro=True)
            return ret

        return run_or_coro(_destroy(folder), as_coro)