Fix an issue where gradient accumulation could not be passed as argum…

…ent due to a type error. (#2910)

nerfstudio/engine/trainer.py

@@ -82,7 +82,7 @@ class TrainerConfig(ExperimentConfig):
     """Path to checkpoint file."""
     log_gradients: bool = False
     """Optionally log gradients during training"""
-    gradient_accumulation_steps: Dict = field(default_factory=lambda: {})
+    gradient_accumulation_steps: Dict[str, int] = field(default_factory=lambda: {})
     """Number of steps to accumulate gradients over. Contains a mapping of {param_group:num}"""