Get this batch as XML

def to_xml(self):
        """Get this batch as XML"""
        assert self.connection != None
        s = '<?xml version="1.0" encoding="UTF-8"?>\n'
        s += '<InvalidationBatch xmlns="http://cloudfront.amazonaws.com/doc/%s/">\n' % self.connection.Version
        for p in self.paths:
            s += '    <Path>%s</Path>\n' % self.escape(p)
        s += '    <CallerReference>%s</CallerReference>\n' % self.caller_reference
        s += '</InvalidationBatch>\n'
        return s