Soft delete implementation

Hi, 

I'm writing a plugin to perform a link between “gherkins datatable header” a Java fields. 

I try to implement a soft delete action. I want that when a java field is deleted, associated gherkins datatable header should be deleted. 

Currently, I defined a PsiReferenceProvider, to add reference between java fields, et gherkins datatable header psi elements. 

Reference works fine, but when I try to do a soft delete, I have a message “Usage of field .... that is not safe to delete”.

I don't find any documentation about this issue and how to solve it.  Can you help me ? 

The plugin source code is available here: https://github.com/deblockt/cucumber-datatable-to-bean-mapping-intelij