Getting the file_id of a photo with Telethon?

Question

Python

I'm creating a Telegram bot and I need to get a file_id, like photos. file_id example:

"AgACAgIAAx0CW7VwqQAD3GE80mUSC6AbGV2lcHFzI5J3me7zAAJwtTEbkWJISbKzPMDueHfrAQADAgADeAADIAQ"

I figured out how to get the file_id of the document:
event.file.id
But if you get photos this way, it gives an error: Is it possible to get the file_id of the photo? If you need more information, please ask. Thank you!
'PhotoSize' object has no attribute 'location'