Something

 def add(self, parent, name, value=None, attrs={}):
 """Produce an xml element e with parent parent, optionally with value v,
and attributes attrs.
If value is specified, it will be placed in the element as a text node.
Returns the generated element."""
  e = etree.SubElement(parent, name, attrs)
  if value is not None:
   e.text = value
  return e