Add assert for max_steps to be positive in MegatronGPTSFTModel (NVIDI…

…A#9110)

Signed-off-by: Abhishree <abhishreetm@gmail.com>

nemo/collections/nlp/models/language_modeling/megatron_gpt_sft_model.py

@@ -74,6 +74,7 @@ def __init__(self, cfg: DictConfig, trainer: Trainer):
             raise ImportError(
                 "Apex was not found. Please see the NeMo README for installation instructions: https://github.com/NVIDIA/NeMo#megatron-gpt."
             )
+        assert trainer.max_steps > 0, "max_steps for SFT can't be negative as its required to build the dataset"
         super().__init__(cfg, trainer=trainer)
         self.sep_id = cfg.get('sep_id', 49704)
         if hasattr(self.cfg.data, "validation_ds"):