我写了一个自定义的lambda函数，需要在dataframe中的groupby操作之后应用。lambda函数将所有唯一字符串连接在一起，并使用适当的joiner，如“，”。我试图在Python的Dask库中实现相同的功能。然而，我得到了下面的错误信息。有人能指导我如何在Dask中实现这个lambda函数吗？

Pandas实现：

A = pd.DataFrame(data = {"A": ["saad", "saad", "saad", "saad", "nimra", "asad", "nimra", "nimra", "asad"],
                         "B": ["hello", "hello", "saad", "whatsup?", "yup", "nup", "saad", "saad", "nup"],
                         "C": ["hello", "hello", "saad", "whatsup?", "yup", "nup", "saad", "saad", "nup"]
                        }
                )
A.groupby("A")["B"].unique().apply(', '. join)
A.groupby("A").agg(lambda s: ', '.join(s.unique()))

This code works perfectly fine and produces the correct output:
        B                       C
A       
asad    nup                     nup
nimra   yup, saad               yup, saad
saad    hello, saad, whatsup?   hello, saad, whatsup?

Dask实现

我尝试在Dask中使用以下代码实现它：
x一个一个一个一个x一个一个二个x