我有一个要解析的xml，进行了一些更改并将其保存到新文件中。它有<?xml version="1.0" encoding="utf-8" standalone="yes"?>我要保留的声明。当我保存新文件时，我失去了standalone="yes"一点。我如何保留它？这是我的代码：

templateXml = """<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<package>
  <provider>Some Data</provider>
  <studio_display_name>Some Other Data</studio_display_name>
</package>"""

from lxml import etree
tree = etree.fromstring(templateXml)

xmlFileOut = '/Users/User1/Desktop/Python/Done.xml'

with open(xmlFileOut, "w") as f:
    f.write(etree.tostring(tree, pretty_print = True, xml_declaration = True, encoding='UTF-8'))