enforce contents of (attribute type)
enforce contents of (attribute type)

Yes, we can declare the type of the `type' slot to be one of the symbols
:CDATA, :ENTITY, :ID, :IMPLIED, :NOTATION, and :TOKEN, but that doesn't
force an error all the time if something else is given.

The printer croaks if we give it a string, so instead of having the
reader turn strings into symbols, which may not always be how attributes
get made, use and around method on `initialize-instance'.

drurowin/data.esis