void setHeaderString(const SbString &str)
Sets the header for output files. This is useful, for example, if you have a file format that is a superset of the Inventor file format and you want Inventor to read the files. It is highly recommend that
in your new header you simply append to the header of the Inventor file format you are extending. For example, if a new file format is based on the Inventor 2.1 file format, register a header similar
to: "#Inventor V2.1 ascii MY FILE FORMAT EXTENSION" Then all Inventor 2.1 applications (and later) can read the file.