# File lib/aws/dynamo_db/item_collection.rb, line 747
      def with_filter attribute, op, *values

        values = values.map {|value| format_attribute_value(value) }

        filter = {
          :attribute_value_list => values,
          :comparison_operator => op
        }

        if scan_filters.key?(attribute)
          raise(ArgumentError, "conflicting filters for attribute #{attribute}")
        end

        refine(:scan_filters => scan_filters.merge(attribute => filter))

      end