Moved Model Card Callback init in Trainer to a separate function (#3047)

* Moved Model Card Callback init in Trainer to a separate function for subclassing

* revert formatting

* Rename slightly; add docstring which'll go in docs

* Initialize default_args_dict before the super().__init__()

---------

Co-authored-by: Tom Aarsen <Cubiegamedev@gmail.com>

sentence_transformers/trainer.py

@@ -277,8 +277,24 @@ def __init__(
             self.eval_dataset = self.maybe_add_prompts_or_dataset_name_column(
                 eval_dataset, args.prompts, dataset_name="eval"
             )
+        self.add_model_card_callback(default_args_dict)
+
+    def add_model_card_callback(self, default_args_dict: dict[str, Any]) -> None:
+        """
+        Add a callback responsible for automatically tracking data required for the automatic model card generation
+
+        This method is called in the ``__init__`` method of the
+        :class:`~sentence_transformers.trainer.SentenceTransformerTrainer` class.
+
+        Args:
+            default_args_dict (Dict[str, Any]): A dictionary of the default training arguments, so we can determine
+                which arguments have been changed for the model card.
+
+        .. note::
+
+            This method can be overriden by subclassing the trainer to remove/customize this callback in custom uses cases
+        """
 
-        # Add a callback responsible for automatically tracking data required for the automatic model card generation
         model_card_callback = ModelCardCallback(self, default_args_dict)
         self.add_callback(model_card_callback)
         model_card_callback.on_init_end(self.args, self.state, self.control, self.model)