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(UserList ul, UserList ul1,UserList ul2 ..)
This function takes 2 or more list-user field types as arguments and returns true if the contents of all the the arguments together, except for the first, are included in the contents of first argument; false otherwise.
Includes ([Assigned To] , [Manager], [Employee])
This will return true if all the users in the Manager field and Employee field are selected for Assigned To field.