src/transformers/models/beit/modeling_beit.py/BeitUperHead/__init__
class BeitUperHead:    def __init__(self, config: BeitConfig) -> None:
        super().__init__()

        self.pool_scales = config.pool_scales  # e.g. (1, 2, 3, 6)
        self.in_channels = [config.hidden_size] * 4  # e.g. [768, 768, 768, 768]
        self.channels = config.hidden_size
        self.align_corners = False
        self.classifier = nn.Conv2d(self.channels, config.num_labels, kernel_size=1)

        # PSP Module
        self.psp_modules = BeitPyramidPoolingModule(
            self.pool_scales,
            self.in_channels[-1],
            self.channels,
            align_corners=self.align_corners,
        )
        self.bottleneck = BeitConvModule(
            self.in_channels[-1] + len(self.pool_scales) * self.channels,
            self.channels,
            kernel_size=3,
            padding=1,
        )
        # FPN Module
        self.lateral_convs = nn.ModuleList()
        self.fpn_convs = nn.ModuleList()
        for in_channels in self.in_channels[:-1]:  # skip the top layer
            l_conv = BeitConvModule(in_channels, self.channels, kernel_size=1)
            fpn_conv = BeitConvModule(self.channels, self.channels, kernel_size=3, padding=1)
            self.lateral_convs.append(l_conv)
            self.fpn_convs.append(fpn_conv)

        self.fpn_bottleneck = BeitConvModule(
            len(self.in_channels) * self.channels,
            self.channels,
            kernel_size=3,
            padding=1,
        )