FAQ Do I have to include methods like " defaults" if I don't use them?

From DANSE

No. The methods _defaults(), _configure(), _init(), and _fini can be omitted safely: these functions all have implementations higher in the hierarchy.

If you do use them, it is now (v. 0.8+) necessary to invoke those methods on the base class:

 def _defaults( self):
    Component._defaults( self)
    ...