add two checks to handle legacy format interleaved multimodal ds (#2721) [skip ci]

* add two checks to handle legacy format interleaved ds

* fix: add warning about multiple image using legacy format

---------

Co-authored-by: NanoCode012 <nano@axolotl.ai>

src/axolotl/processing_strategies.py

@@ -1,5 +1,6 @@
 """Module containing ProcessingStrategy classes and its derivative for different MultiModal Model types"""
 
+import logging
 from copy import deepcopy
 from typing import Optional
 
@@ -9,6 +10,8 @@ from torch import Tensor
 from transformers import ProcessorMixin
 from transformers.image_utils import load_image
 
+LOG = logging.getLogger(__name__)
+
 
 class ProcessingStrategy:
     """Base Processing Strategy class"""
@@ -112,7 +115,9 @@ class ProcessingStrategy:
                 )
 
             processed_example = None
-            if "messages" in example:  # OpenAI format
+            if (
+                "messages" in example and example["messages"] is not None
+            ):  # OpenAI format
                 processed_example = example
             else:  # Legacy format
                 processed_example = convert_legacy_format(example)
@@ -132,10 +137,17 @@ class ProcessingStrategy:
                     break
 
             # if the image key exists, add the image to the first message
-            if image_key is not None:
+            if image_key is not None and processed_example[image_key] is not None:
                 # TODO: check if it's normal to be single image only for common datasets
                 # From observation, it's usually a list of single image but some datasets may have several columns for images
                 # Temporary solution: take the first image and suggest people convert their datasets to use multi-content Messages
+                if len(processed_example[image_key]) > 0:
+                    LOG.warning(
+                        f"Found {len(processed_example[image_key])} images in a sample. Using the first one."
+                        "If you are using a dataset with multiple images per sample, please convert it to use multi-content Messages."
+                        "See https://docs.axolotl.ai/docs/multimodal.html#dataset-format"
+                    )
+
                 image_value = processed_example[image_key][0]
 
                 # Handle image loading (Image, url, path, base64)