<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def clear(self):
 """Remove all key-value pairs."""

        for i in range(self.maxlevel):
            self._head[2+i] = self._tail
            self._tail[-1] = 0
        self._level = 1