case tensorflow::AttrValue::kList:
      metadata.is_list = 1;
      metadata.list_size = 0;
      metadata.total_size = -1;
#define LIST_CASE(field, attr_type, ...)              \
  if (attr->list().field##_size() > 0) {              \
    metadata.type = attr_type;                        \
    metadata.list_size = attr->list().field##_size(); \
    __VA_ARGS__;                                      \