Function switch_xml_get 

pub unsafe extern "C" fn switch_xml_get(
    xml: switch_xml_t,
    ...
) -> switch_xml_t

\brief Traverses the switch_xml structure to retrieve a specific subtag. Takes a \ variable length list of tag names and indexes. The argument list must be \ terminated by either an index of -1 or an empty string tag name. Example: \ title = switch_xml_get(library, “shelf”, 0, “book”, 2, “title”, -1); \ This retrieves the title of the 3rd book on the 1st shelf of library. \ Returns NULL if not found. \param xml the xml node \return an xml node or NULL