What is Stream.ObjectInvariant()?

[colejohnson66]

There's an obsoleted protected method on Stream, ObjectInvariant():

runtime/src/libraries/System.Private.CoreLib/src/System/IO/Stream.cs

Lines 944 to 945 in e6f1fd8

	[Obsolete("Do not call or override this method.")]
	protected virtual void ObjectInvariant() { }

What was its purpose? The documentation says that it serves to "provide[s] support for a Contract", but how? Contract.Invariant wants a boolean but this method returns nothing.

[elgonzo]

See here for some more info on how this kind of method was supposed to be used/implemented in the past: https://learn.microsoft.com/en-us/dotnet/framework/debug-trace-profile/code-contracts#invariants