'Bind to widgets with bindtag CLASSNAME at event
SEQUENCE a call of function FUNC. An additional
boolean parameter ADD specifies whether FUNC will be
called additionally to the other bound function or
whether it will replace the previous function. See bind for
the return value.'

def bind_class(self, className, sequence=None, func=None, add=None):

    return self._bind(('bind', className), sequence, func, add, 0)
