For compatibility reasons, we quite often convert completely unmanaged
instances to `ILive`s so they fit the required parameters of a property
or method call. This ensures such cases will not cause any issues when
trying to interact with the underlying data.
Originally I had this allowing write operations, but that seems a bit
unsafe (when performing a write one would assume that the underlying
data is being persisted, whereas in this case it is not). We can change
this if the requirements change in the future, but I think throwing is
the safest bet for now.
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