def filter_params
      @_filter_params ||=
        case params[:filter]
        when Hash, ActionController::Parameters
          default_filters.each_with_object({}) do |field, hash|
            unformatted_field = @request.unformat_key(field)
            hash[unformatted_field] = params[:filter][field]
          end
        end
    end
def filter_params
      @_filter_params ||=
        case params[:filter]
        when Hash, ActionController::Parameters
          default_filters.each_with_object({}) do |field, hash|
            unformatted_field = @request.unformat_key(field)
            hash[unformatted_field] = params[:filter][field]
          end
        end
    end
Build a Hash with the default filters.

 @return [Hash, NilClass]

 @api public