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db.properties.aggregate([{$group:{_id:{addedBy:"$addedBy",properties:"$propertyType"},v:{$push:"$$ROOT"},k:{$first:"$propertyType"}}},{$group:{_id:"$_id.addedBy",properties:{$push:{k:"$k",v:"$v"}}}},{$project:{addedBy:"$_id",_id:0,properties:{$arrayToObject:"$properties"}}}])