无法从另一个文件导入由WTF创建的表单

Question

我正在尝试在forms.py文件中导入使用Flask-WTF创建的表单，但由于某些原因，我遇到导入错误：

ImportError: cannot import name 'Permission' from 'website.forms' (C:\Users\moti9\Desktop\website\website\forms.py)

我当时在想也许我有一个循环导入问题，但是我似乎找不到问题，因为我可以从完全相同的文件中导入另一种表格。

forms.py：

from wtforms.validators import DataRequired, length, email, equal_to, ValidationError
from wtforms import StringField, PasswordField, BooleanField, RadioField, SubmitField
from flask_wtf import FlaskForm
from flask_wtf.file import file_allowed, FileField

class Registration(FlaskForm):
    alredy_exist='alredy exists,  if you alredy have a user press' #a message to present when a Unique validator activates
    username = StringField('Username:', validators=[DataRequired(), length(min=4, max=20), Unique(User.username, db.session, message='Username {}'.format(alredy_exist))])
    email = StringField('Email', validators=[DataRequired(), email(), Unique(User.email, db.session, message='Email {}'.format(alredy_exist))])
    password = PasswordField('Password:', validators=[DataRequired(), length(min=6, max=12)])
    #repeat_password = PasswordField('Repeat password',  validators=[equal_to('password', 'passwords must match')])
    submit = SubmitField('Register')

class Permission(FlaskForm):
    create_post = BooleanField('create_post')
    delete_post = BooleanField('delete_post')
    edit_post = BooleanField('edit_post')
    delete_user = BooleanField('delete user')
    view_scripts = BooleanField('view_scripts')
    admin = BooleanField('admin')

我可以导入Registration，但不能导入权限，而我只是想不明白为什么。

谢谢。