Steps to reproduce:

1. Have a template with LLD rule with graph prototype.
2. Have a host with different LLD rule with graph prototype of the same name (and different item prototype keys).
3. Link the template described in step 1 to the host described in step 2.

Result:

The error occurred "Graph "<graph name>" already exists on "<host name>."

Expected:

No error. The graph prototype should be successfully inherited since the graph prototypes are unique in scope of its LLD rule.