Need better documentation for XMLNode.WriiteContent

This really needs to be a bit clearer in terms of what these methods will output.

What is the expected output of the final method "root.WriteContentTo(writer)" for example?

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#### Document Details

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* ID: 9a3b573b-6427-0b34-f970-347dc439b3cf
* Version Independent ID: 3d8d49d7-6efb-86e5-4562-059785893bca
* Content: [XmlNode.WriteContentTo(XmlWriter) Method (System.Xml)](https://docs.microsoft.com/en-us/dotnet/api/system.xml.xmlnode.writecontentto?view=netframework-4.7.2)
* Content Source: [xml/System.Xml/XmlNode.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Xml/XmlNode.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**