Flask Login System: user_loader attribute not found

I'm trying to create a simple login with flask. Unfortunately, I getting the following message when I try to start the website:

@login.user_loader AttributeError: 'function' object has no attribute 'user_loader'

I have 3 files. main.py which handles routing and app start. forms.py which stores my forms and models.py. I assume the error is eighter in main.py or models.py. Attached the project structure. project structure printscreen

main.py

from flask import Flask
app = Flask(__name__)
from flask_login import LoginManager
from flask import render_template, flash, redirect, url_for, request
from flask_login import login_user, logout_user, current_user, 
login_required
import forms
import models
import os

login = LoginManager(app)  # is this here the problem?
login.login_view = 'login' # is this here the problem?


@app.route('/login', methods=['GET', 'POST'])
def login():

    if current_user.is_authenticated:
         return render_template('index.html')
    form = forms.LoginForm()
    if form.validate_on_submit():
        user = models.User()
        user = user.get_user(form.username.data)
        if user is None or not user.check_password(form.password.data):
            flash('Invalid username or password')
            return redirect(url_for('login'))
        login_user(user, remember=form.remember_me.data)
        print(request.values)
        next_page = url_for('index')
        return redirect(next_page)

    return render_template('login.html', title='Sign In', form=form)


if __name__ == "__main__":
    app.secret_key = os.urandom(12)
    app.run(debug=True, host='0.0.0.0', port=4000)

models.py

from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash
import os
import pypyodbc
import pymssql
from main import login

class User(UserMixin):

    id = None
    username = None
    email = None
    password_hash = None
    exits = False

    dbhost = 'XX'
    dbusername = 'XX'
    dbpassword = 'XX'
    dbdatabase = 'XX'
    isUbuntu = False
    connectionstring = ''
    paramUserName = ""

    if os.name != 'nt':
        isUbuntu = True

    if isUbuntu == False:
        connectionstring = 'Driver={SQL Server};Server=localhost;Database=PMC'

    if isUbuntu == True:
        connection = pymssql.connect(dbhost, dbusername, dbpassword, dbdatabase)
    else:
        connection = pypyodbc.connect(connectionstring)


    def __repr__(self):
        return '<User {}>'.format(self.username)

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def get_user(self, User):
        cursor = self.connection.cursor()
        SQLCommand = ('Select * from  [UserData] where username=(%d)')
        Values = User
        cursor.execute(SQLCommand, Values)
        user = cursor.fetchone()
        self.connection.close()
        if user is not None:
            self.id = user[0]
            self.username = user[1]
            self.email = user[2]
            self.password_hash = user[3]
            self.exits = True
            return self
        else:
            return None

    def get_userwithid(self, ID):
        cursor = self.connection.cursor()
        SQLCommand = ('Select * from  [UserData] where id=(%d)')
        Values = ID
        cursor.execute(SQLCommand, Values)
        user = cursor.fetchone()
        self.connection.close()
        if user is not None:
            self.id = user[0]
            self.username = user[1]
            self.email = user[2]
            self.password_hash = user[3]
            self.exits = True
            return self
        else:
            return None
    def check_password(self, password):
        return check_password_hash(self.password_hash, password)


@login.user_loader # this here throws the error
def load_user(id):
    user = User()
    user = user.get_userwithid(id)
    return user