def prev_key(self, key, default=_sentinel):
        """Get predecessor to key, raises KeyError if key is min key
        or key does not exist.
        """
        item = self.prev_item(key, default)
        return default if item is default else item[0]
def prev_key(self, key, default=_sentinel):
        """Get predecessor to key, raises KeyError if key is min key
        or key does not exist.
        """
        item = self.prev_item(key, default)
        return default if item is default else item[0]
def prev_key ( self , key , default = _sentinel ) : item = self . prev_item ( key , default ) return default if item is default else item [ 0 ]
Get predecessor to key, raises KeyError if key is min key
        or key does not exist.
Get predecessor to key raises KeyError if key is min key or key does not exist .