Symfony, is there a way to detect if a Relation is being used?

Question

symfony

Hello everyone, unfortunately I did not know how to describe the task in the heading.

I have several tables such as for example: vat (value added tax, etc.), they have relation to other tables.
I need to write an api where the VAT sheet is issued:

[
    {
        "id":1,
        "tax":20,
        "deletable": true
    }
]

If VAT was linked somewhere, for example, to goods, services, etc... Then it should be issued ("deletable": false):

[
    {
        "id":1,
        "tax":20,
        "deletable": false
    }
]

are there any ideas how to fix this?