How to add smart value in the hidden summary field of an issue using the the post functions script

[Marta Rogalinska]

Hello,

I'm trying to automatically create a "Summary" based on a CustomField selected by the creator. 

"[POOL] - Deletion requested" where [POOL] is the value selected by the creator of the ticket - this is a multi-choice "Labels" type field.

The Summary field is hidden to the creator.

We are trying to use the following Jython post function script:

from com.atlassian.jira.component import ComponentAccessor

customFieldManager = ComponentAccessor.getCustomFieldManager()
poolCustomField = customFieldManager.getCustomFieldObject(12314)
pool = issue.getCustomFieldValue(poolCustomField)

issue.setSummary("[" + pool + "] - Deletion requested")

but I am getting an error when creating the ticket.

1. is it because the field is a multi-choice label field?

2. is it possible to use a smart value in such a Jython script, if yes - how?

I've successfully used the smart value {{Issue.fields.customfield_12314}} in the same ticket creation so the CF exists.

Thank you for your help.

Marta