Hyperopt NoneType object has no attribute 'randint'

Question

I'm facing some problems using hyperopt

# Here we use a single parameter grid, and execute just one iteration
space = _set_space(parameters_grid)

trials = hyperopt.Trials()
best_params = hyperopt.fmin(fn=_loss_fnc,
                            space=space,
                            algo=hyperopt.tpe.suggest,
                            max_evals=1,
                            rstate=np.random.RandomState(42),
                            timeout=None,
                            trials=trials)
best_params = hyperopt.space_eval(space, best_params)
best_params_idx = np.argmin(trials.losses())

# If the default parameter used in grid is not good, we try again with a bigger grid
if abs(trials.losses()[best_params_idx] < abs(min_score):
    space = _set_space(full_parameters_grid)  # updates the space
    best_params = hyperopt.fmin(fn=_loss_fnc,
                                space=space,
                                algo=hyperopt.tpe.suggest,
                                max_evals=5,
                                rstate=np.random.RandomState(42),
                                timeout=None,
                                trials=trials,
                                loss_threshold=min_score)

best_params = hyperopt.space_eval(space, best_params)


def _set_space(parameters_grid):
    # Just some rules to define the which parameters to include in the grid
    parameters_grid = _update_grid(parameters_grid)

    # processing to hyperopt's format
    search_space = _normalize_for_hyperopt(parameters_grid)
    space = hyperopt.hp.choice('a', list(search_space.values()))
    return space

But it returns the following error:

ERROR in rec_eval
EXCEPTION <class 'AttributeError'> 'NoneType' object has no attribute 'randint'
NODE
0 randint
1   Literal{1}

================================================================================
ERROR: Error while computing regression for bundle 13380
Traceback (most recent call last):
  File "/my_file/optimizer.py", line 225, in fit
    best_params = hyperopt.space_eval(space, trials.argmin)
  File "/usr/local/lib/python3.7/site-packages/hyperopt/fmin.py", line 585, in space_eval
    rval = pyll.rec_eval(space, memo=memo)
  File "/usr/local/lib/python3.7/site-packages/hyperopt/pyll/base.py", line 911, in rec_eval
    rval = scope._impls[node.name](*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/hyperopt/pyll/stochastic.py", line 103, in randint
    return rng.randint(low, high, size)
AttributeError: 'NoneType' object has no attribute 'randint'
ERROR: 'NoneType' object has no attribute 'randint'

Do you have any ideas what the problem shoud be? The model runs without any problem, but when executing space_eval, it crashes.

Also, it is related with the second spaceclass assigned inside the second attempt, because the code runs without any problems if we ommit it.