It seems that you have chosen the wrong list (TeamMember) where it should be Account.
A bit more context might help actually :)
While creation of object, you are trying to assign Team Member Entity list object to Account reference object. That is why you are getting this error.
Hi Roy and Steffy, thank you for much for commenting over here.
I wanted to create a notifications where I need to associate the ‘Account’ objects with ‘Notifications’ object in the Domain model.
However, I have chosen the wrong Multiplicity, now the issue solved.