examples/research_projects/lxmert/modeling_frcnn.py/LastLevelP6P7/__init__
class LastLevelP6P7:    def __init__(self, in_channels, out_channels):
        super().__init__()
        self.num_levels = 2
        self.in_feature = "res5"
        self.p6 = nn.Conv2d(in_channels, out_channels, 3, 2, 1)
        self.p7 = nn.Conv2d(out_channels, out_channels, 3, 2, 1)