fix required instance_column and image_column cast

Author: davidberenstein1957

examples/dreambooth/train_dreambooth_lora_flux.py

@@ -308,7 +308,7 @@ def parse_args(input_args=None):
         "--instance_prompt",
         type=str,
         default=None,
-        required=True,
+        required=False,
         help="The prompt with identifier specifying the instance, e.g. 'photo of a TOK dog', 'in the style of TOK'",
     )
     parser.add_argument(
@@ -714,7 +714,7 @@ def __init__(
         # we load the training data using load_dataset
         if args.dataset_name is not None:
             try:
-                from datasets import load_dataset
+                from datasets import load_dataset, Image
             except ImportError:
                 raise ImportError(
                     "You are trying to load your data using the datasets library. If you wish to train using custom "
@@ -742,6 +742,8 @@ def __init__(
                     raise ValueError(
                         f"`--image_column` value '{args.image_column}' not found in dataset columns. Dataset columns are: {', '.join(column_names)}"
                     )
+                    
+            dataset["train"] = dataset["train"].cast_column(image_column, Image(decode=True))
             instance_images = dataset["train"][image_column]
 
             if args.caption_column is None:
@@ -768,7 +770,7 @@ def __init__(
 
             instance_images = [Image.open(path) for path in list(Path(instance_data_root).iterdir())]
             self.custom_instance_prompts = None
-
+        
         self.instance_images = []
         for img in instance_images:
             self.instance_images.extend(itertools.repeat(img, repeats))
@@ -784,6 +786,7 @@ def __init__(
             ]
         )
         for image in self.instance_images:
+            
             image = exif_transpose(image)
             if not image.mode == "RGB":
                 image = image.convert("RGB")