# File lib/aws/policy.rb, line 486
      def filter_conditions(conditions = @conditions)
        conditions.inject({}) do |m, (op, keys)|
          m[op] = keys.inject({}) do |m2, (key, value)|
            m2[key] = value if !block_given? or yield(op, key, value)
            m2
          end
          m.delete(op) if m[op].empty?
          m
        end
      end