def indent_xml(elem, level=0) -> None:
  """Indents and newlines the XML for better output."""
  indent_str = '\n' + level * '  '
  if len(elem):  # pylint: disable=g-explicit-length-test  # `if elem` not valid
    if not elem.text or not elem.text.strip():
      elem.text = indent_str + '  '
    if not elem.tail or not elem.tail.strip():
      elem.tail = indent_str
    for elem in elem:
      indent_xml(elem, level + 1)

                                 n_ask_attempts=_DEFAULT_PROMPT_ASK_ATTEMPTS):
  """Loop over user prompts for an ENV param until receiving a valid response.

  For the env param var_name, read from the environment or verify user input
  until receiving valid input. When done, set var_name in the environ_cp to its
  new value.

  Args:
    environ_cp: (Dict) copy of the os.environ.