'Get the value for a key, either from the album or the item.
Raise a KeyError for invalid keys.'

def _get(self, key):

    if (self.for_path and (key in self.album_keys)):
        return self._get_formatted(self.album, key)
    elif (key in self.model_keys):
        return self._get_formatted(self.model, key)
    elif (key in self.album_keys):
        return self._get_formatted(self.album, key)
    else:
        raise KeyError(key)
