| class  | MongoSessionDataStore | MongoSessionDataStore
 The document model is an outer object that contains the elements:
 
 "id"      : session_id 
 "created" : create_time 
 "accessed": last_access_time 
 "maxIdle" : max_idle_time setting as session was created 
 "expiry"  : time at which session should expire 
 "valid"   : session_valid 
 "context" : a nested object containing 1 nested object per context for which the session id is in use
 
 Each of the nested objects inside the "context" element contains:
 
 unique_context_name : nested object containing name:value pairs of the session attributes for that context
 unique_context_name: vhost:contextpath, where no vhosts="0_0_0_0", root context = "", contextpath "/" replaced by "_"
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