Cannot pass null for targetNamespace to XmlSchemaSet.Add (string targetNamespace, string schemaUri);

For this overload: public System.Xml.Schema.XmlSchema Add (string targetNamespace, string schemaUri);

I have found the following statement sentence to not be true WRT the use of null...
"The schema targetNamespace property, or null to use the targetNamespace specified in the schema."

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* ID: 4052f4bb-b8ca-c523-ce2a-77847134a3e1
* Version Independent ID: f0dfec92-12ca-0a5c-51a9-1c2bfbbd2a2a
* Content: [XmlSchemaSet.Add Method (System.Xml.Schema)](https://docs.microsoft.com/en-us/dotnet/api/system.xml.schema.xmlschemaset.add?view=netframework-4.7.2#System_Xml_Schema_XmlSchemaSet_Add_System_String_System_String_)
* Content Source: [xml/System.Xml.Schema/XmlSchemaSet.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Xml.Schema/XmlSchemaSet.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**