# File lib/aws/core/policy.rb, line 488
        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