fix python 3.11 compatibility

Author: Tuan Tran

lcm/train/two_tower_diffusion_lcm/criterion.py

@@ -33,7 +33,9 @@ class TowerDiffusionLCMCriterionConfig(LCMCriterionConfig):
        Note that this requires the model to be set with
        `trained_with_cf_guidance = True`!
     """
-    step_sampling: StepsSamplerConfig = field(default_factory=lambda: StepsSamplerConfig())
+    step_sampling: StepsSamplerConfig = field(
+        default_factory=lambda: StepsSamplerConfig()
+    )
 
     log_losses_per_timestep_bucket: bool = False