Question about data joining to the same model
The problem is a bad manifestation of a bug that occurs when you have a field named "model". I probably need to make Peewee raise an error if this occurs, but this fixes things:

```python

class Car(Model):
    model_ = CharField(column_name='model', max_length=50, unique=True)
    ...
``` Thanks. That's worked
I have the following code:
```
from datetime import datetime, date

from peewee import *

db = SqliteDatabase(':memory:')


class Car(Model):
    model = CharField(max_length=50, unique=True)
    manufactured = DateField()

    class Meta:
        database = db

    def __str__(self):
        return f'Car: {self.model}'


class Person(Model):
    name = CharField(max_length=100)
    main_car = ForeignKeyField(Car)
    helper_car = ForeignKeyField(Car, on_delete='SET NULL')

    class Meta:
        database = db

    def __str__(self):
        return f'Person: {self.name}'


db.create_tables([Car, Person])

Person.insert(
    name="test",
    main_car=Car.create(model='Mitsubishi', manufactured=datetime.today()),
    helper_car=Car.create(model='BMW', manufactured=date(2001, 12, 12))
).execute()

MainCar = Car.alias()
HelperCar = Car.alias()

print(tuple(
    Person.
        select(Person, MainCar, HelperCar)
        .join(MainCar, on=Person.main_car)
        .switch(Person)
        .join(HelperCar, on=Person.helper_car)
    )
)
```
but when i'm trying to execute this i'm getting an empty tuple in results.
So i tried to execute generated SQL query from that and everything is OK and data returned
```
sqlite> SELECT "t1"."id", "t1"."name", "t1"."main_car_id", "t1"."helper_car_id", "t2"."id", "car" AS "t3", "t2"."manufactured", "t4"."id", "car" AS "t3", "t4"."manufactured" FROM "person" AS "t1" INNER JOIN "car" AS "t2" ON ("t1"."main_car_id" = "t2"."id") INNER JOIN "car" AS "t4" ON ("t1"."helper_car_id" = "t4"."id");
1|test|1|2|1|car|2021-03-15|2|car|2001-12-12
sqlite> 
```

What am i doing wrong?