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db.collection.aggregate([{$group:{_id:{class:"$class",type:"$type",color:"$color"},v:{$push:{filed1:"$filed1",field2:"$field2"}}}},{$group:{_id:{class:"$_id.class",type:"$_id.type"},docs2:{$push:{k:"$_id.color",v:"$v"}}}},{$group:{_id:"$_id.class",docs3:{$push:{k:"$_id.type",v:{$arrayToObject:"$docs2"}}}}},{$replaceWith:{$mergeObjects:[{_id:"$_id"},{$arrayToObject:"$docs3"}]}}])