Problems getting file id in start script

Hello,

Currently I use BonitaStudio 7.7.4 and I have a human task with a form with multiple data to which a file can be loaded.

Create a multiple document that takes its value from the variable declared in the contract.
I want for each multiple record to store the id of the document so that in the next task I can show each multiple data in a table with its associated document.

I am using this code within each:
Document doc = apiAccessor.getProcessAPI().getDocument(processInstanceId, currentComisionMensualDetalleInput.documentoAsociado).getId();

In the log it shows me the following error:
org.bonitasoft.engine.api.impl.ProcessAPIImpl.getDocument() is applicable for argument types: (java.lang.Long, org.bonitasoft.engine.bpm.contract.FileInputValue) values: [6003, FileInputValue{fileName='Documento.pdf'}]

I appreciate your help in this inconvenience that I am having.
Thank you