def Kml(nodes):
  """Returns a tuple representing a KML Document node.

  Args:
    nodes: Iterable of child nodes representing top-level KML objects.

  Returns:
    Tuple for pyfo to produce the <kml> node.
  """
  return ('kml', ('Document', nodes),
          dict(xmlns='http://www.opengis.net/kml/2.2'))