def safe_hash
      Hash[map do |key, value|
        if Protocol::RESERVED_KEYS.include?(key)
          nil
        elsif value.is_a?(Hash) &&
              value[Protocol::KEY_TYPE] == Protocol::TYPE_RELATION
          nil
        elsif value.nil?
          [key, Protocol::DELETE_OP]
        else
          [key, Parse.pointerize_value(value)]
        end
      end.compact]
    end
def safe_hash
      Hash[map do |key, value|
        if Protocol::RESERVED_KEYS.include?(key)
          nil
        elsif value.is_a?(Hash) &&
              value[Protocol::KEY_TYPE] == Protocol::TYPE_RELATION
          nil
        elsif value.nil?
          [key, Protocol::DELETE_OP]
        else
          [key, Parse.pointerize_value(value)]
        end
      end.compact]
    end
representation of object to send on saves