<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def key(self, key, strictkey=None):
 """ Return a chunk referencing a key in a mapping with the name 'key'. """

        return self._select(self._pointer.key(key, strictkey))