how to create subcollection in mongodb code example

Example: mongodb create collection

db.createCollection( ,
   {
     capped: ,
     autoIndexId: ,
     size: ,
     max: ,
     storageEngine: ,
     validator: ,
     validationLevel: ,
     validationAction: ,
     indexOptionDefaults: ,
     viewOn: ,              // Added in MongoDB 3.4
     pipeline: ,          // Added in MongoDB 3.4
     collation: ,         // Added in MongoDB 3.4
     writeConcern: 
   }
)