Um exemplo de models.py com Relationships many to many

exemple_models.py

### Example: https://gist.github.com/souzaux/c652508e0ae05adaf7cb/edit
from catwatch.blueprints.user.models import User
from catwatch.blueprints.device.models import Device


user_device = db.Table('user_device',
    db.Column('user_id', db.Integer, db.ForeignKey('users.user_id')),
    db.Column('device_id', db.Integer, db.ForeignKey('devices.device_id'))
)

class User(UserMixin, ResourceMixin, db.Model):

    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    
    # Relationships.
    devices = db.relationship("Device", secondary=user_device, back_populates="devices")


class Device(ResourceMixin, db.Model):
    __tablename__ = 'devices'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128), nullable=False)
    uniqueid = db.Column(db.String(128), unique=True,
                                        nullable=False,
                                        index=True)
    status = db.Column(db.String(128))
    
    # Relationships.
    users = db.relationship("User", secondary=user_device, back_populates="users")

from catwatch.lib.util_sqlalchemy import ResourceMixin
from catwatch.extensions import db

from catwatch.blueprints.user.models import User

class Device(ResourceMixin, db.Model):

__tablename__ = 'devices'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(128), nullable=False)
uniqueid = db.Column(db.String(128), unique=True, nullable=False, index=True)
status = db.Column(db.String(128))

# Relationships many to many
user = db.relationship('User', secondary=user_device, back_populates='users')

import datetime
from collections import OrderedDict
from hashlib import md5

import pytz
from flask import current_app

from flask_login import UserMixin

from itsdangerous import URLSafeTimedSerializer,
TimedJSONWebSignatureSerializer

from sqlalchemy import or_
from catwatch.lib.util_sqlalchemy import ResourceMixin, AwareDateTime
from catwatch.blueprints.billing.models.credit_card import CreditCard
from catwatch.blueprints.billing.models.subscription import Subscription
from catwatch.blueprints.billing.models.invoice import Invoice
from catwatch.extensions import db, bcrypt

from catwatch.blueprints.device.models import Device

user_device = db.Table('user_device',
db.Column('user_id', db.Integer, db.ForeignKey('users.user_id')),
db.Column('device_id', db.Integer, db.ForeignKey('devices.device_id'))
)

class User(UserMixin, ResourceMixin, db.Model):
ROLE = OrderedDict([
('guest', 'Guest'),
('member', 'Member'),
('admin', 'Admin')
])

__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)

# Relationships.
credit_card = db.relationship(CreditCard, uselist=False, backref='users',
                              passive_deletes=True)
subscription = db.relationship(Subscription, uselist=False,
                               backref='users', passive_deletes=True)
invoices = db.relationship(Invoice, backref='users', passive_deletes=True)

# Relationships many to many.
device = db.relationship('Device', secondary=user_device, back_populates='devices')

Traceback (most recent call last):
File "/Users/guilherme/.virtualenvs/catwatch/bin/run", line 9, in
load_entry_point('commands==1.0', 'console_scripts', 'run')()
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 664, in call
return self.main(_args, *_kwargs)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 643, in main
with self.make_context(prog_name, args, **extra) as ctx:
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 560, in make_context
self.parse_args(ctx, args)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 951, in parse_args
echo(ctx.get_help(), color=ctx.color)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 416, in get_help
return self.command.get_help(self)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 772, in get_help
self.format_help(ctx, formatter)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 787, in format_help
self.format_options(ctx, formatter)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 892, in format_options
self.format_commands(ctx, formatter)
File "/Users/guilherme/.virtualenvs/catwatch/lib/python2.7/site-packages/click/core.py", line 937, in format_commands
cmd = self.get_command(ctx, subcommand)
File "/Users/guilherme/Projetos/website/cli/cli.py", line 38, in get_command
None, None, ['cli'])
File "/Users/guilherme/Projetos/website/cli/commands/cmd_add.py", line 28, in
from catwatch.app import create_app
File "/Users/guilherme/Projetos/website/catwatch/app.py", line 4, in
from catwatch.blueprints.user.models import User
File "/Users/guilherme/Projetos/website/catwatch/blueprints/user/init.py", line 1, in
from catwatch.blueprints.user.views import user
File "/Users/guilherme/Projetos/website/catwatch/blueprints/user/views.py", line 17, in
from catwatch.blueprints.user.models import User
File "/Users/guilherme/Projetos/website/catwatch/blueprints/user/models.py", line 22, in
from catwatch.blueprints.device.models import Device
File "/Users/guilherme/Projetos/website/catwatch/blueprints/device/models.py", line 6, in
from catwatch.blueprints.user.models import User
ImportError: cannot import name User