'Call decision_function on the estimator with the best found parameters.
Only available if ``refit=True`` and the underlying estimator supports
``decision_function``.
Parameters
X : indexable, length n_samples
Must fulfill the input assumptions of the
underlying estimator.'

@if_delegate_has_method(delegate=('best_estimator_', 'estimator'))
def decision_function(self, X):

    return self.best_estimator_.decision_function(X)
