'If any kwarg is None, get it from case attributes.'

def __init__(self, case, clear_selector=None, dropdown_selector=None, field_name=None, input_selector=None, label_selector=None, labels_selector=None, model=None, option_selector=None, widget_selector=None):

    self.case = case
    self.clear_selector = (clear_selector or self.case.clear_selector)
    self.dropdown_selector = (dropdown_selector or self.case.dropdown_selector)
    self.field_name = (field_name or self.case.field_name)
    self.input_selector = (input_selector or self.case.input_selector)
    self.label_selector = (label_selector or self.case.label_selector)
    self.labels_selector = (labels_selector or self.case.labels_selector)
    self.model = (model or self.case.model)
    self.option_selector = (option_selector or self.case.option_selector)
    self.widget_selector = (widget_selector or self.case.widget_selector)
    self.field_container_selector = (u'fieldset.aligned    .field-%s' % self.field_name)
    self.field_selector = (u'#id_%s' % self.field_name)
    self.field_clear_selector = (u'%s    %s' % (self.field_container_selector, self.clear_selector))
    self.in_popup = False
