Currently, exporting a single host that has dependencies on another host (e.g., items used in graphs or triggers) does not produce any warning. The export goes through, but on import, restoring data is impossible without also importing the other related host.

Steps to reproduce:

1. Create two hosts: A (with item A) and B (with item B)  A_and_B_hosts.yaml
2. On Host A, create a graph or trigger that also includes an item from Host B
3. Export Host A only A_host.yaml
4. Export Host B only B_host.yaml
5. Delete A and B hosts
6. Import the exported files

Actual result:
Hosts imported without trigger. No warning was shown during export that part of the configuration have dependencies and will not be restorable

Expected result: Show a warning during export "some elements (e.g. graphs, triggers) reference other hosts or templates that are not included in the export. These elements may be lost during import."