title: Define Python class in separate file
body: <pre><code># File 1
  me = MongoEngine(app) # I want to use my instance of MongoEngine to define new classes like the example in File 2
  
  # File 2
  class Book(me.Document):
      title = StringField(null=False, unique=True)
      year_published = IntField(null=True)
  </code></pre>
  
  <p>How can i pass the instance <code>me.Document</code> as an Object definition when creating my new classes in a new file. It works if i put them in the same file?</p>