Solved by mariosasko in post #2 
              
              
                Hi, 
this line is the problem: 
X_data = Dataset(X_text_tokenized)

because X_text_tokenized is a list of dictionaries and not a dictionary of lists. You can fix this with the following code: 
def list_of_dicts_to_dict_of_lists(d):
    dic = d[0]
    keys = dic.keys()
    values = [dic.values() for …