node_exporter can't retrieve metrics for DRBD 9.X

Host operating system: output of uname -a

Linux 3.10.0-1127.el7.x86_64 #1 SMP Tue Mar 31 23:36:51 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

node_exporter version: output of node_exporter --version

node_exporter, version 1.0.1 (branch: HEAD, revision: 3715be6ae899f2a9b9dbfd9c39f3e09a7bd4559f)
build user: root@1f76dbbcfa55
build date: 20200616-12:44:12
go version: go1.14.4

node_exporter command line flags

--collector.drbd

Are you running node_exporter in Docker?

No

What did you do that produced an error?

Installed DRBD 9.0.22
Configured node_exporter with --collector.drbd flag

What did you expect to see?

Metrics like node_drbd_*

What did you see instead?

Don't see metrics related to node_drbd_*

Notes:

Regarding to the: https://www.linbit.com/drbd-user-guide/drbd-guide-9_0-en/ (4.2.3. Status information in /proc/drbd) - drbd 9.x version doesn't provide live statistics by virtual file /proc/drbd.
Now this functionality is outdated and output looks like:

[user@<host name> ~]# cat /proc/drbd
version: 9.0.22-2 (api:2/proto:86-116)
GIT-hash: 719792f2cc1360c65c848ffdb66090959e27fde5 build by mockbuild@, 2020-04-05 03:16:50
Transports (api:16): tcp (9.0.22-2)

Start with the --collector.drbd entry point and compare its current /proc/drbd expectations with the DRBD 9 output shown in the issue. Run node_exporter with the flag against a DRBD 9 system; done means the expected node_drbd_* metrics are exposed.