This method can be used to fill all empty fields with the same value.
A field is empty when is value is None, NotLoaded or NotAvailable.
Example:
# It will be impossible to get all empty fields, except
# of 'url' (with a call to fillobj())
video.set_empty_fields(NotAvailable, ('url',))
When you want to add a field to your CapBaseObject derivated class, use
this method to:
- add it in the fields list (order is important)
- set the only possible values types
- default value to NotLoaded if not specified
- possibility to set another value
