How to use the fvcore.nn.weight_init.c2_xavier_fill function in fvcore

output_norm = get_norm(norm, out_channels)

            lateral_conv = Conv2d(
                in_channels, out_channels, kernel_size=1, bias=use_bias, norm=lateral_norm
            )
            output_conv = Conv2d(
                out_channels,
                out_channels,
                kernel_size=3,
                stride=1,
                padding=1,
                bias=use_bias,
                norm=output_norm,
            )
            weight_init.c2_xavier_fill(lateral_conv)
            weight_init.c2_xavier_fill(output_conv)
            stage = int(math.log2(in_strides[idx]))
            self.add_module("fpn_lateral{}".format(stage), lateral_conv)
            self.add_module("fpn_output{}".format(stage), output_conv)

            lateral_convs.append(lateral_conv)
            output_convs.append(output_conv)
        # Place convs into top-down order (from low to high resolution)
        # to make the top-down computation in forward clearer.
        self.lateral_convs = lateral_convs[::-1]
        self.output_convs = output_convs[::-1]
        self.top_block = top_block
        self.in_features = in_features
        self.bottom_up = bottom_up
        # Return feature names are "p", like ["p2", "p3", ..., "p6"]
        self._out_feature_strides = {"p{}".format(int(math.log2(s))): s for s in in_strides}
        # top block output feature maps.

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)
        for module in [self.p6, self.p7]:
            weight_init.c2_xavier_fill(module)

)
            self.add_module("conv{}".format(k + 1), conv)
            self.conv_norm_relus.append(conv)
            self._output_size = (conv_dim, self._output_size[1], self._output_size[2])

        self.fcs = []
        for k in range(num_fc):
            fc = nn.Linear(np.prod(self._output_size), fc_dim)
            self.add_module("fc{}".format(k + 1), fc)
            self.fcs.append(fc)
            self._output_size = fc_dim

        for layer in self.conv_norm_relus:
            weight_init.c2_msra_fill(layer)
        for layer in self.fcs:
            weight_init.c2_xavier_fill(layer)

lateral_norm = get_norm(norm, out_channels)
            output_norm = get_norm(norm, out_channels)

            lateral_conv = Conv2d(
                in_channels, out_channels, kernel_size=1, bias=use_bias, norm=lateral_norm
            )
            output_conv = Conv2d(
                out_channels,
                out_channels,
                kernel_size=3,
                stride=1,
                padding=1,
                bias=use_bias,
                norm=output_norm,
            )
            weight_init.c2_xavier_fill(lateral_conv)
            weight_init.c2_xavier_fill(output_conv)
            stage = int(math.log2(in_strides[idx]))
            self.add_module("fpn_lateral{}".format(stage), lateral_conv)
            self.add_module("fpn_output{}".format(stage), output_conv)

            lateral_convs.append(lateral_conv)
            output_convs.append(output_conv)
        # Place convs into top-down order (from low to high resolution)
        # to make the top-down computation in forward clearer.
        self.lateral_convs = lateral_convs[::-1]
        self.output_convs = output_convs[::-1]
        self.top_block = top_block
        self.in_features = in_features
        self.bottom_up = bottom_up
        # Return feature names are "p", like ["p2", "p3", ..., "p6"]
        self._out_feature_strides = {"p{}".format(int(math.log2(s))): s for s in in_strides}