style: add BitsAndBytesConfig __repr__ function (#24331)

* style: add repr to BitsAndBytesConfig
Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>

* chore: update pattern for __repr__

implement diff dict for __repr__ of BitsAndBytesConfig
Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>

---------
Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>

src/transformers/utils/quantization_config.py

@@ -228,3 +228,46 @@ class BitsAndBytesConfig:
         output["bnb_4bit_compute_dtype"] = str(output["bnb_4bit_compute_dtype"]).split(".")[1]
 
         return output
+
+    def __repr__(self):
+        return f"{self.__class__.__name__} {self.to_json_string()}"
+
+    def to_json_string(self, use_diff: bool = True) -> str:
+        """
+        Serializes this instance to a JSON string.
+
+        Args:
+            use_diff (`bool`, *optional*, defaults to `True`):
+                If set to `True`, only the difference between the config instance and the default `PretrainedConfig()`
+                is serialized to JSON string.
+
+        Returns:
+            `str`: String containing all the attributes that make up this configuration instance in JSON format.
+        """
+        if use_diff is True:
+            config_dict = self.to_diff_dict()
+        else:
+            config_dict = self.to_dict()
+        return json.dumps(config_dict, indent=2, sort_keys=True) + "\n"
+
+    def to_diff_dict(self) -> Dict[str, Any]:
+        """
+        Removes all attributes from config which correspond to the default config attributes for better readability and
+        serializes to a Python dictionary.
+
+        Returns:
+            `Dict[str, Any]`: Dictionary of all the attributes that make up this configuration instance,
+        """
+        config_dict = self.to_dict()
+
+        # get the default config dict
+        default_config_dict = BitsAndBytesConfig().to_dict()
+
+        serializable_config_dict = {}
+
+        # only serialize values that differ from the default config
+        for key, value in config_dict.items():
+            if value != default_config_dict[key]:
+                serializable_config_dict[key] = value
+
+        return serializable_config_dict