ValueError: Found array with dim 4. Estimator expected ＜= 2.

python3: ValueError: Found array with dim 4. Estimator expected <= 2.

原因：维度不匹配。数组维度为4维，现在期望的是 <= 2维

方法：改为二维形式。

本人这里是4维度，我改为个数为两维度，如下处理：

 source_x = (source_x.reshape(source_x.shape[0], source_x.shape[1] * source_x.shape[2] * source_x.shape[3]))
 target_x = (target_x.reshape(target_x.shape[0], target_x.shape[1] * target_x.shape[2] * target_x.shape[3]))