Xamarin.Mac has two classes: CICmykHalftone : CIFilter and CICMYKHalftone : CICmykHalftone. (Note "CMYK" vs "Cmyk"). This is legal C#. An mdoc update generates:
<Type Name="CICmykHalftone" FullName="CoreImage.CICmykHalftone">
<TypeSignature Language="C#" Value="public class CICmykHalftone : CoreImage.CIFilter" />
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<Base>
<BaseTypeName>CoreImage.CIFilter</BaseTypeName>
<BaseTypeName FrameworkAlternate="xamarin-macos-sdk-14">CoreImage.CICmykHalftone</BaseTypeName>
</Base>
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This defines a recursive inheritance, which breaks Ecma2Yaml with an OutOfMemoryException.