keep in mind this is not a query. the intention is a 'bulk-update' 
do you have a suggestion how to remove a property in this operation.

I hesitated using the `+=` sign maybe a   `<=`  or `*=`  would express this better?

IMHO changing the existing  `=`  to a `:=` implying a replace and using the `=` for a 'merge' would be better, but that's a more 'breaking'