def post_body_init(self):
        '''Initializes the part of algorithm needing a body to exist first.'''
        self.body = self.agent.nanflat_body_a[0]  # single-body algo
        # create the extra replay memory for SIL
        memory_name = self.memory_spec['sil_replay_name']
        MemoryClass = getattr(memory, memory_name)
        self.body.replay_memory = MemoryClass(self.memory_spec, self, self.body)
        self.init_algorithm_params()
        self.init_nets()
        logger.info(util.self_desc(self))

# ...
    def sample(self):
        '''Modify the onpolicy sample to also append to replay'''
        batches = [body.memory.sample() for body in self.agent.nanflat_body_a]
        batch = util.concat_batches(batches)
        data_keys = self.body.replay_memory.data_keys
        for idx in range(len(batch['dones'])):
            tuples = [batch[k][idx] for k in data_keys]
            self.body.replay_memory.add_experience(*tuples)
        batch = util.to_torch_batch(batch, self.net.gpu)
        return batch

    def replay_sample(self):
        '''Samples a batch from memory'''
        batches = [body.replay_memory.sample() for body in self.agent.nanflat_body_a]
        batch = util.concat_batches(batches)
        batch = util.to_torch_batch(batch, self.net.gpu)
        assert not torch.isnan(batch['states']).any()
        return batch