Get the default value that will be used for a specific instance.

        Args:
            obj (HasProps) : The instance to get the default value for.

        Returns:
            object

def instance_default(self, obj):
        ''' Get the default value that will be used for a specific instance.

        Args:
            obj (HasProps) : The instance to get the default value for.

        Returns:
            object

        '''
        return self.property.themed_default(obj.__class__, self.name, obj.themed_values())