def set_published_date(self, published_date=None):
pass<EOL>
Sets the published date.

        arg:    published_date (osid.calendaring.DateTime): the new
                published date
        raise:  InvalidArgument - ``published_date`` is invalid
        raise:  NoAccess - ``Metadata.isReadOnly()`` is ``true``
        raise:  NullArgument - ``published_date`` is ``null``
        *compliance: mandatory -- This method must be implemented.*