module ActiveAdmin::Inputs::FilterBase

def collection_from_options
  if options[:collection].is_a?(Proc)
    template.instance_eval(&options[:collection])
  else
    super
  end
end

def input_wrapping(&block)
  template.content_tag :div, template.capture(&block), wrapper_html_options
end

def required?
  false
end

def wrapper_html_options
  { :class => "filter_form_field #{as}" }
end