RelatedJoin allows adding item several times

Perhaps it is by design but I was kind of surprised to see that if I have

class x(SQLObject):
    ys = RelatedJoin( 'y' )

class y(SQLObject):
    ....

then I'm allowed to add several times the same 'y' object to 'x' via

myx = x.get( 1 )
myy = y.get( 1 )
x.addY( myy )
x.addY( myy )
x.addY( myy )

Is there a keyword argument to RelatedJoin or to addY that forbids this?
Or I have to code this myself, i.e. check if an object is already
added, and if yes, refuse to do it?

Cheers,
Daniel



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