# Codeblock 7
NUM_ANCHORS = 3

class RPN(nn.Module):
    def __init__(self):
        super().__init__()
        
        self.intermediate = nn.Conv2d(in_channels=256, out_channels=256, kernel_size=3, padding=1)
        
        self.cls = nn.Conv2d(in_channels=256, out_channels=NUM_ANCHORS*2, kernel_size=1)
        self.reg = nn.Conv2d(in_channels=256, out_channels=NUM_ANCHORS*4, kernel_size=1)
    
    def forward(self, x):
        x = self.intermediate(x)
        
        objectness_scores = self.cls(x)
        bbox_regressions  = self.reg(x)
        
        return objectness_scores, bbox_regressions