Add root node to xml

[snippsat]

But I want to add header and root node so the my output looks like:

You use library that deal with this as ndc85430 posted,i always use BS | lxml for task like this like.
Example.

from bs4 import BeautifulSoup

xml = '''\
<values>
    <item>
       <A>1</A>
       <B>a</B
   </item>
   <item>
       <A>2</A>
       <B>b</B>
   </item>
   <item>
       <A>3</A>
       <B>c</B>
   </item>
</values>'''

soup = BeautifulSoup(xml, "xml")
# Make headertag
new_tag = soup.new_tag("header")
soup.select_one('values').insert_before(new_tag)

# Append sub tag to header tag
header_tag = soup.select_one('header')
new_tag1 = soup.new_tag("names")
new_tag1.string = "test"
header_tag.append(new_tag1)
print(soup)

Output:
<?xml version="1.0" encoding="utf-8"?>
<header>
  <names>test</names>
</header>
<values>
  <item>
    <A>1</A>
    <B>a</B>
  </item>
  <item>
    <A>2</A>
    <B>b</B>
  </item>
  <item>
    <A>3</A>
    <B>c</B>
  </item>
</values>