<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def wrap(self, string, width):
 """ Wrap lines according to width Place '\n' whenever necessary """

        if not string or width <= 0:
            logging.error("invalid string: %s or width: %s" % (string, width))
            return False

        tmp = ""
        for line in string.splitlines():
            if len(line) <= width:
                tmp += line + "\n"
                continue

            cur = 0
            length = len(line)
            while cur + width < length:
                cur = line[:cur+width].rfind(self.sep) + len(self.sep) - 1
                line = line[:cur] + "\n" + line[cur+1:]

            tmp += line + "\n\n"

        return tmp