对着SEBlock的代码啊吧啊吧

偶尔忘记的时候再来看看怎么实现（）

from paddle.nn import *

class SELayer(Layer):
    def __init__(self, channel, reduction=16):
        super(SELayer, self).__init__()
        self.avg_pool = AdaptiveAvgPool2D(output_size=[None, None])
        self.fc = Sequential(
            Linear(channel, channel // reduction, bias_attr=False),
            ReLU(),
            Linear(channel // reduction, channel, bias_attr=False),
            Sigmoid()
        )

    def forward(self, x):
        b, c, _, _ = x.size()
        y = self.avg_pool(x).view(b, c)
        y = self.fc(y).view(b, c, 1, 1)
        return x * y.expand_as(x)