How to filter the sender name correctly and use it in the titel_template?

[ZzenlD]

Hello everyone,
I would like to forward messages by email and customize the title as follows: [<sender name>] <title>

This means I have to filter the sender name from $from. My attempt looks like this:

configs:
  <target-here>:
    urls:
      - mailtos://<mail-destination>
    mailrise:
      title_template: "[${from.split('<')[0].strip()}] ${subject}"

smtp:
  hostname: mailrise.my.domain
  auth:
    basic:
      <username>: <password>

Unfortunately, this does not work. ${subject} is resolved, but the required part is not.

Does anyone have any idea why this might be, or how I can fix it?

EDIT: For example, if the sender is Nextcloud <nextcloud.my.domain>, the title should be [Nextcloud] ${subject}.

Thanks a lot

[ZzenlD]

I'm not quite sure how python template should be used here. Does anyone have another example so that I can derive my use case from it?