When the method `Testissue#addLink` adds a link with relationship `backport by`, it also adds a link with the same relationship to the reversed issue. It is wrong because the relationship of the reversed link should be `backport of` instead of the `backport by`.

This problem also occurs at many other relations which don't have the same name. What I know is shown below:

- `backported by` and `backport of`
- `csr for` and `csr of`
- `blocks` and `is blocked by`
- `clones` and `is cloned by`

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I find this bug when I read the code of the test `BackportsTests#mainIssue`. Fixing this bug may influence many test cases so it needs more investigation before solving it.