def push(self, kv):
if kv[<NUM_LIT:0>] in self: <EOL><INDENT>self.__delitem__(kv[<NUM_LIT:0>])<EOL><DEDENT>self.__setitem__(kv[<NUM_LIT:0>], kv[<NUM_LIT:1>])<EOL>
Adds a new item from the given (key, value)-tuple.
            If the key exists, pushes the updated item to the head of the dict.