Flask-security：如何显示所有角色而不仅仅是 current_users 角色MongoEngine

如何解决Flask-security：如何显示所有角色而不仅仅是 current_users 角色MongoEngine

我有一个注册/添加用户页面，我希望能够在创建用户时将角色附加到用户。我不知道的是如何显示所有角色。我可以获得 current_user.roles 但由于它不是当前用户而是要创建的用户，因此我想显示 user_datastore 中的所有角色。

模型.py

class Role(db.Document,RoleMixin):
    def __str__(self):
        return self.name
    name = db.StringField(max_length=80,unique=True)
    description = db.StringField(max_length=255)
    permissions = db.StringField(max_length=255)

class User(db.Document,UserMixin):
    def __str__(self):
        return self.username

    username = db.StringField(max_length=255)
    password = db.StringField(max_length=255)
    active = db.BooleanField(default=True)
    fs_uniquifier = db.StringField(max_length=64,unique=True)
    confirmed_at = db.DateTimeField()
    current_login_at = db.DateTimeField()
    last_login_at = db.DateTimeField()
    current_login_ip = db.StringField(max_length=255)
    last_login_ip = db.StringField(max_length=255)
    login_count = db.IntField(max_length=255)
    roles = db.ListField(db.ReferenceField(Role),default=[])

auth.py

@auth.route('/register',methods=['POST','GET'])
def register():
    if request.method == 'POST':
        if not user_datastore.find_user(username=request.form.get('username')):
            user_datastore.create_user(username=request.form.get('username'),password=hash_password(request.form.get('password')))
        else:
            flash("User already exists.")
        return redirect(url_for('main.index'))
    return render_template('security/register_user.html')

register_user.html

{% include "security/_messages.html" %}
<div class="login">
    <h1>Add user</h1>
    <form method="post">
        <input type="text" name="username" placeholder="Username" required="required" />
        <input type="password" name="password" placeholder="Password" required="required" />
        <button type="submit" class="btn btn-primary btn-block btn-large">Add user.</button>
    </form>
</div>