Retrieve data from UserDictionary.Set (string key, IEnumerable<double> val)

To store a list of values I’m using UserDictionary.Set (string key, IEnumerable val), but I cannot find how to retrieve the data later on. Any examples?
Thanks

  1. https://developer.rhino3d.com/api/RhinoCommon/html/P_Rhino_DocObjects_Custom_UserDictionary_Dictionary.htm

  2. https://developer.rhino3d.com/api/RhinoCommon/html/T_Rhino_Collections_ArchivableDictionary.htm

  3. https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.idictionary-2?view=netcore-3.1

    var valueOfKey = myUserDic.Dictionary[someExistingKey];