旧版本中：
from keras.layers import merge
merge6 = merge([layer1,layer2], mode = 'concat', concat_axis = 3)
新版本中：
from keras.layers.merge import concatenate
merge = concatenate([layer1, layer2], axis=3)
旧版本中：
from keras.layers import merge
merge6 = merge([layer1,layer2], mode = 'concat', concat_axis = 3)
新版本中：
from keras.layers.merge import concatenate
merge = concatenate([layer1, layer2], axis=3)