def cell_input_fn(inputs,attention):
        if not self.use_residual:
            return array_ops.concat([inputs,attention],-1)

        att_projection=layers.Dense(self.hidden_units,
                                    dtype=tf.float32,
                                    use_bias=False,
                                    name='attention_cell_input_fn')
        return att_projection(array_ops.concat[inputs,attention],-1)

    cell=AttentionWrapper(
        cell=cell,
        attention_mechanism=self.attention_mechanism,
        attention_layer_size=self.hidden_units,
        alignment_history=alignment_history,
        cell_input_fn=cell_input_fn,
        name='Attention_Wrapper'
    )

这段代码中att_projection是layers.Dense生成的一个对象吗，返回att_projection(array_ops.concat[inputs,attention],-1)是什么意思，对象还能再传参吗。
cell中传入内部函数cell_input_fn，那么函数的参数inputs,attention在哪里传进去。