UID is a unique, non-human-readable identifier for a content object which stays on the object even if the object is moved.
Plone uses UIDs for
警告
Dexterity content framework does not use UIDS, but integer ids (intids) to manage references.
Use UID() accessor function:
>>> site.events.UID()
'ce380ef0f10a85beb864025928e1819b'
Use lookupObject() in reference catalog.
>>> site.reference_catalog.lookupObject('ce380ef0f10a85beb864025928e1819b')
<ATBTreeFolder at /test/events>
None will be returned if there is content item with matching UID (the item has been deleted).