I got this error but unluckily can not trace back to my code. What can be the possible reasons for this failure? Thanks!

My observation space initialization is as follows:

```
def init_obs_space(self):
observation_space_n = []
for i in range(self.num_agents):
lb = np.zeros(self.num_vertices * 2)
ub = np.concatenate((
np.ones(self.num_vertices),
np.full(self.num_vertices, self.num_bins)
))
if i >= self.num_adversaries:
lb = np.concatenate((
lb, np.zeros(self.num_vertices + 1)
))
ub = np.concatenate((
ub, np.full(self.num_vertices, self.num_bins)
))
ub = np.concatenate((
ub, np.full(1, self.def_budget)
))
observation_space_n.append(
spaces.Box(lb, ub) # TODO: update this to be upper bounded by the number of adversaries
)
return observation_space_n
```