The method is wrapped in a nn.Module (e.g., Linear8bitLt, Linear4bit), and the quantized linear layer should have the following definition:

class Linear4bit(nn.Module):
    def init(self, ):
        
def forward(self, x):
    return my_4bit_kernel(x, self.weight, self.bias)

This way, Transformers models can be easily quantized by replacing some instances of nn.Linear with a target class.