How can I return a text fragment from an XPath function?

from lxml import etree

def myFunc(context, parm):
  import lxml.html
  return lxml.html.fragments_fromstring('some sample <em>text</em>')
  #em = etree.Element('em')
  #em.text = 'text'
  #return ['some sample ', em]

myns = etree.FunctionNamespace('http://example.org/myNamespace')
myns['my-func'] = myFunc

xslt = '''
    <xsl:stylesheet version="1.0"
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
        xmlns:myns="http://example.org/myNamespace">
      <xsl:template match="/">
        <xsl:variable name="result" select="myns:my-func(./*)" />
        <xsl:for-each select="$result">
          <xsl:copy-of select="." />
        </xsl:for-each>
      </xsl:template>
    </xsl:stylesheet>
'''

root = etree.XML('<root></root>')
doc = etree.ElementTree(root)
transform = etree.XSLT(etree.XML(xslt))
res = transform(doc)
print(res)