<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def runs_to_xml(self, runSet, runs, blockname=None):
 """ This function creates the XML structure for a list of runs """

        # copy benchmarkinfo, limits, columntitles, systeminfo from xml_header
        runsElem = util.copy_of_xml_element(self.xml_header)
        runsElem.set("options", " ".join(runSet.options))
        if blockname is not None:
            runsElem.set("block", blockname)
            runsElem.set("name", ((runSet.real_name + ".") if runSet.real_name else "") + blockname)
        elif runSet.real_name:
            runsElem.set("name", runSet.real_name)

        # collect XMLelements from all runs
        for run in runs:
            runsElem.append(run.xml)

        return runsElem