def parse_course_key(course_identifier):
try:<EOL><INDENT>course_run_key = CourseKey.from_string(course_identifier)<EOL><DEDENT>except InvalidKeyError:<EOL><INDENT>return course_identifier<EOL><DEDENT>return quote_plus('<STR_LIT:U+0020>'.join([course_run_key.org, course_run_key.course]))<EOL>
Return the serialized course key given either a course run ID or course key.