def add_class2fields(self, html_class, fields=[], exclude=[], include_all_if_empty=True):
        """
        add class to html widgets.
        """
        self.add_attr2fields('class', html_class, fields, exclude)
def add_class2fields ( self , html_class , fields = [ ] , exclude = [ ] , include_all_if_empty = True ) : self . add_attr2fields ( 'class' , html_class , fields , exclude )
add class to html widgets.