<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def Get(self, key):
 """Fetch the object from cache. Objects may be flushed from cache at any time. Callers must always handle the possibility of KeyError raised here. Args: key: The key used to access the object. Returns: Cached object. Raises: KeyError: If the object is not present in the cache. """

    if key not in self._hash:
      raise KeyError(key)

    node = self._hash[key]

    self._age.Unlink(node)
    self._age.AppendNode(node)

    return node.data