<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def expand_relative_uri(self, context, uri):
 """If uri is relative then expand in context. Prints warning if expansion happens. """

        full_uri = urljoin(context, uri)
        if (full_uri != uri):
            print("  WARNING - expanded relative URI to %s" % (full_uri))
            uri = full_uri
        return(uri)