docs: def prettystr(subtree):
      """Print an element tree with nice indentation.
  
      Prettyprinting a whole VOEvent often doesn't seem to work, probably for
      issues relating to whitespace cf.
      http://lxml.de/FAQ.html#why-doesn-t-the-pretty-print-option-reformat-my-xml-output
      This function is a quick workaround for prettyprinting a subsection
      of a VOEvent, for easier desk-checking.
  
      Args:
          subtree(:class`lxml.etree.ElementTree`): A node in the VOEvent element tree.
      Returns:
          str: Prettyprinted string representation of the raw XML.
      """
      subtree = deepcopy(subtree)
      lxml.objectify.deannotate(subtree)
      lxml.etree.cleanup_namespaces(subtree)
      return lxml.etree.tostring(subtree, pretty_print=True).decode(
          encoding="utf-8")