Unclear documentation of Property bag entity types

Please amend the code example under "Property bag entity types" to include how instances of a property bag could be added to the context and how they are queried. I spent hours trying to understand how this works, but I keep getting the following error no matter what I try:

Cannot create a DbSet for 'Dictionary' because it is configured as an shared type entity type. Access the entity type via the `Set` method overload that accepts an entity type name

I see this as a documentation shortcoming. More elaborate example is required.

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* ID: 550a3c36-7f1d-efa7-3ed8-769720168da4
* Version Independent ID: 627c4301-e00d-826e-d545-3a244305dec9
* Content: [Shadow and Indexer Properties - EF Core](https://docs.microsoft.com/en-us/ef/core/modeling/shadow-properties)
* Content Source: [entity-framework/core/modeling/shadow-properties.md](https://github.com/dotnet/EntityFramework.Docs/blob/main/entity-framework/core/modeling/shadow-properties.md)
* Product: **entity-framework**
* Technology: **entity-framework-core**
* GitHub Login: @AndriySvyryd
* Microsoft Alias: **avickers**