Is there a new function in 5.8 for saveAttributeForm()

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I am upgrading from 5.7.5.13 to the current 5.8. The site uses ProEvents and I am having trouble figuring out how to bring that addon up to speed with 5.8. When I try to add or update an event I receive this error...
Call to undefined method Concrete\Core\Entity\Attribute\Key\PageKey::saveAttributeForm()
Is there a new function in 5.8 that handles this?
The error occurs in...
/packages
/proevents
/src
/Models
/Event.php

Thanks in advance.
C