fix: change file opening mode to append for metadata file in generate_images function

sample.py

@@ -33,7 +33,7 @@ def generate_images(api_type: str, benchmarks: List[str]):
                         entry = json.loads(line)
                         existing_metadata[entry["filepath"]] = entry
 
-            with open(metadata_file, "w") as f:
+            with open(metadata_file, "a") as f:
                 for metadata, folder_name in tqdm(
                     benchmark,
                     desc=f"Generating images for {benchmark_type}",
@@ -78,7 +78,7 @@ def generate_images(api_type: str, benchmarks: List[str]):
                         entry = json.loads(line)
                         existing_metadata[entry["filepath"]] = entry
 
-            with open(metadata_file, "w") as f:
+            with open(metadata_file, "a") as f:
                 for prompt, image_path in tqdm(
                     benchmark,
                     desc=f"Generating images for {benchmark_type}",