output_json_key_string
output_json_key_string(out, false, 5, "symbol", al->sym->name);
output_json_key_string(out, false, 5, "dso", dso_name);
output_json_key_string(out, true, 3, "comm", thread__comm_str(al.thread));
output_json_key_string(out, true, 3, fields[i]->name, s.buffer);
output_json_key_string(out, true, 2, "captured-on", buf);
output_json_key_string(out, true, 2, "hostname", env->hostname);
output_json_key_string(out, true, 2, "os-release",
output_json_key_string(out, true, 2, "arch", env->arch);
output_json_key_string(out, true, 2, "cpu-desc", env->cpu_desc);
output_json_key_string(out, true, 2, "cpuid", env->cpuid);
output_json_key_string(out, true, 2, "perf-version", env->version);