World size must be larger than number of experts in MoE inference ?

As the comments depict, does DeepSpeed require that the device number must be larger than the number of experts, necessarily? According to the source code, it seems like that #experts could be larger than the world size, yet the if branch could never be reached.

# deepspeed/inference/engine.py
def _create_ep_parallel_group(self, moe_experts):
    # Call the init process
    self.ep_group = {}
    self.expert_mp_group = {}
    moe_experts = moe_experts if type(moe_experts) is list else [moe_experts]
    for e in moe_experts:
        self.ep_group.update({e: None})
        self.expert_mp_group.update({e: None})
    for moe_ep_size in self.ep_group.keys():
        # If dist.get_world_size() is smaller than moe_ep_size (say world_size = 2 and moe_ep_size = 8), num_ep_groups is 0
        num_ep_groups = dist.get_world_size() // moe_ep_size
        for i in range(num_ep_groups):
            ep_cnt = i * moe_ep_size
            # If dist.get_world_size() is smaller than moe_ep_size, this if branch is useless
            size = dist.get_world_size() if moe_ep_size > dist.get_world_size() else moe_ep_size
            ranks = list(range(ep_cnt, ep_cnt + size))
            _ep_group = dist.new_group(ranks)
            if dist.get_rank() in ranks:
                self.ep_group.update({moe_ep_size: _ep_group})

        if dist.get_world_size() > moe_ep_size:
            num_expert_mp_groups = dist.get_world_size() // num_ep_groups
            expert_mp_size = dist.get_world_size() // moe_ep_size
            for i in range(num_expert_mp_groups):
                expert_mp_comm_ranks = [i + nr * moe_ep_size for nr in range(expert_mp_size)]
                _expert_mp_group = dist.new_group(expert_mp_comm_ranks)
                if dist.get_rank() in expert_mp_comm_ranks:
                    self.expert_mp_group.update({moe_ep_size: _expert_mp_group})

Start in deepspeed/inference/engine.py at _create_ep_parallel_group and trace how world size and the expert parallel size determine the groups. Verify the behavior when the world size is smaller than the number of experts, then establish whether the current branch and group construction support that configuration; done means the supported relationship and resulting behavior are clear.