Python module and __all__ -

I am trying to understand how to manage the module with __all . For example, I have a structured code:

  main.py | = & Gt; / Database | = & Gt; __init__.py | = & Gt; Engine (with variable engine, session, etc.)   
 I want to be able to import directly  session  and  engine  examples Like the  database  module:  
  from the database import session   
 I tried to add the line  __ All__ = ['Sessions']  or  __ all__ = ['engine.session']  to  __init__py  but when I try to import, one exception to me  AttributeError: ' 
   
  
  
 
 text "itemprop =" text " > 
  __Ell __  does not list names, by itself, imports items in a module if you  database import * to  syntax.  
 import  session If you use the  database / __ init__ in , then this is the list name to import from that module .gi :   from .ignin Import Sessions