title: how to initialise a peewee.Model object? __init__() doesn't work
body: <p>I am not able to initialise the fields of a "peewee.Model" descendant object with the usual <strong>init</strong>() method. How can I initialise alternatively?</p>
  
  <pre><code>import peewee
  
  peewee_database = peewee.SqliteDatabase('example.db')
  
  class Config():
  
      def __init__(self, seats, cylinders):
          self.seats = seats
          self.cylinders = cylinders
  
  class Car(peewee.Model):
  
      magic_number = peewee.IntegerField()
      color = peewee.TextField()
  
      class Meta:
          database = peewee_database
  
      def __init__(self, config):
          self.magic_number = config.seats / config.cylinders
          self.color = None
  
  peewee_database.connect()
  peewee_database.create_tables([Car])
  
  config = Config(7, 6)
  car = Car(config)
  car.color = "blue"
  car.save()
  </code></pre>
  
  <p>produces this error in Python3:</p>
  
  <pre><code>  File "test.py", line 27, in &lt;module&gt;
      car = Car(config)
    File "test.py", line 20, in __init__
      self.magic_number = config.seats / config.cylinders
    File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/peewee.py", line 3764, in __set__
      instance.__data__[self.name] = value
    TypeError: 'NoneType' object does not support item assignment
  </code></pre>
  
  <p>help! :)</p>