switch (attr->value_case()) {
#define SINGLE_CASE(kK, attr_type, size_expr) \
  case tensorflow::AttrValue::kK:             \
    metadata.is_list = 0;                     \
    metadata.list_size = -1;                  \
    metadata.type = attr_type;                \
    metadata.total_size = size_expr;          \
    break;

    SINGLE_CASE(kS, TF_ATTR_STRING, attr->s().length());