# Codeblock 7a
class YOLOv2(nn.Module):
    def __init__(self):
        super().__init__()
        
        self.darknet = Darknet()                       #(1)
        
        self.passthrough = ConvBlock(512, 64, 1, 0)    #(2)
        
        self.stage6 = nn.ModuleList([                  #(3)
            ConvBlock(1024, 1024, 3, 1), 
            ConvBlock(1024, 1024, 3, 1), 
        ])

        self.stage7 = nn.ModuleList([
            ConvBlock(1280, 1024, 3, 1),
            ConvBlock(1024, NUM_ANCHORS*(5+NUM_CLASSES), 1, 0)    #(4)
        ])