'Write xml report
:return: None'

def _write_xml_to_file(self):

    self._open_file()
    self._xml.appendChild(self._top_elem)
    try:
        self._xml.writexml(self._file, addindent=('    ' * 4), newl='\n', encoding='UTF-8')
        self._file.flush()
    finally:
        self._file.close()
