如何从Saxon的扩展函数返回文档节点？

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.lib.ExtensionFunctionCall;
import net.sf.saxon.lib.ExtensionFunctionDefinition;
import net.sf.saxon.om.DocumentInfo;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.SequenceType;

public class MyExtensionFunction extends ExtensionFunctionDefinition {

    @Override
    public StructuredQName getFunctionQName() {
        return new StructuredQName("my", "http://example.com/my-extension", "returnDocumentNode");
    }

    @Override
    public SequenceType[] getArgumentTypes() {
        return new SequenceType[] {};
    }

    @Override
    public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
        return SequenceType.SINGLE_NODE;
    }

    @Override
    public ExtensionFunctionCall makeCallExpression() {
        return new ExtensionFunctionCall() {
            @Override
            public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
                // 创建文档节点
                DocumentInfo doc = createDocumentNode();

                // 返回文档节点
                return doc;
            }
        };
    }

    private DocumentInfo createDocumentNode() {
        // 在这里创建文档节点，可以使用Saxon提供的DocumentBuilder等类来解析XML文件或构建XML文档
        // 示例代码：
        // DocumentBuilder builder = context.getConfiguration().getDocumentBuilder();
        // DocumentInfo doc = builder.build(new File("path/to/xml"));

        return null; // 返回创建的文档节点
    }
}