<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pop(self, key, default=_marker):
 """remove the item by key If not default is specified, raise KeyError if nothing could be removed. Return 'default' if specified and nothing could be removed """

        try:
            popped = self[key]
            del self[key]
            return popped
        except KeyError:
            if default == _marker:
                raise
            return default