def set_pkg_desc(self, doc, text):
self.assert_package_exists()<EOL>if not self.package_desc_set:<EOL><INDENT>self.package_desc_set = True<EOL>doc.package.description = text<EOL><DEDENT>else:<EOL><INDENT>raise CardinalityError('<STR_LIT>')<EOL><DEDENT>
Set's the package's description.
        Raises CardinalityError if description already set.
        Raises OrderError if no package previously defined.