How to compute multiple-classes roc_auc in MNE

When I attempte to compute the roc_auc after a multiple classfication problem, the MNE give the error
" raise ValueError('roc_auc scoring can only be computed for ’
ValueError: roc_auc scoring can only be computed for two-class problems."
If I want to achive this, how should I do?
Thanks,

roc_auc is not a score well defined for multi-class problems. It’s a fundamental problem
not just an implementation problem

Alex