Python3.x 聚合(aggregate)为最多包含两个元素的列表

给出如下用户表:

   user       query
0    a1      orange
1    a1  strawberry
2    a1        pear
3    a2      orange
4    a2  strawberry
5    a2       lemon
6    a3      orange
7    a3      banana
8    a6        meat
9    a7        beer
10   a8       juice

我想按user分组，并将其汇总为query的列表，然后 Select 前两项，如果超过两项，则预期结果为

  user                        query
0   a1         [orange, strawberry]
1   a2         [orange, strawberry]
2   a3             [orange, banana]
3   a6                       [meat]
4   a7                       [beer]
5   a8                      [juice]

使用下面的代码

df_user = pd.DataFrame( {'user': {0: 'a1', 1: 'a1', 2: 'a1', 3: 'a2', 
                                  4: 'a2', 5: 'a2', 6: 'a3', 7: 'a3', 
                                  8: 'a6', 9: 'a7', 10: 'a8'}, 
                         'query': {0: 'orange', 1: 'strawberry', 
                                   2: 'pear', 3: 'orange', 4: 'strawberry', 
                                   5: 'lemon', 6: 'orange', 7: 'banana', 
                                   8: 'meat', 9: 'beer', 10: 'juice'}} )

print(df_user.groupby(['user'], as_index=False).agg(list))

我设法得到了

  user                        query
0   a1   [orange, strawberry, pear]
1   a2  [orange, strawberry, lemon]
2   a3             [orange, banana]
3   a6                       [meat]
4   a7                       [beer]
5   a8                      [juice]

获得理想结果的好方法是什么？