Instantiate the model

def instantiate(self, **extra_args):
        """ Instantiate the model """
        input_block = self.input_block.instantiate()
        backbone = self.backbone.instantiate(**extra_args)

        return QRainbowModel(
            input_block=input_block,
            backbone=backbone,
            action_space=extra_args['action_space'],
            vmin=self.vmin,
            vmax=self.vmax,
            atoms=self.atoms,
            initial_std_dev=self.initial_std_dev,
            factorized_noise=self.factorized_noise
        )