src/transformers/models/transfo_xl/modeling_tf_transfo_xl.py/TFTransfoXLMainLayer/build
class TFTransfoXLMainLayer:    def build(self, input_shape):
        if not self.untie_r:
            self.r_w_bias = self.add_weight(
                shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_w_bias"
            )
            self.r_r_bias = self.add_weight(
                shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_r_bias"
            )
        super().build(input_shape)