def METHOD_NAME(self):
    """
    Provides an grade according to the answer of a student using the list
    saved during the last call to self.remind()
    """
    score = 0
    if len(self._answer) != len(self.items):
        for e in self.items:
            e["css"] = "error-state anim-fade"
        return 0
    for i, e in enumerate(self._answer):
        self.items[i]['css'] = 'success-state anim-fade'
        score += 1
        if self.items[i]['id'] != e:
            self.items[i]['css'] = 'error-state anim-fade'
            score -= 1
    return score / len(self._answer)