<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def check_url_data (self, url_data):
 """Check one URL data instance."""

        if url_data.url is None:
            url = ""
        else:
            url = url_data.url.encode("ascii", "replace")
        self.setName("CheckThread-%s" % url)
        check_url(url_data, self.logger)