This example shows how to create VL annotations file using subfolder structure, each subfolder is the class label.
The root folder of the dataset contains 3 subfolders which are the classes: Ulcer, Normal and AVM. 
import os  
import csv

def create_annotation_csv(root_dir, output_csv):  
    rows = []

    # Iterate over all items in the root directory.
    for subdir in os.listdir(root_dir):
        subdir_path = os.path.join(root_dir, subdir)
        if os.path.isdir(subdir_path):
            label = subdir  # The subfolder name is the label.
            # Iterate over each file in the subdirectory.
            for filename in os.listdir(subdir_path):
                file_path = os.path.join(subdir_path, filename)
                if os.path.isfile(file_path):
                    # Build the relative file path (e.g., "b/image1.jpg").
                    relative_path = os.path.join(subdir, filename)
                    rows.append([relative_path, label])

    # Write the CSV file with header "filename,label".
    with open(output_csv, mode='w', newline='') as csv_file:
        writer = csv.writer(csv_file)
        writer.writerow(['filename', 'label'])
        writer.writerows(rows)
    print(f"CSV file '{output_csv}' created successfully.")

if __name__ == "__main__":  
    root_directory = "."  # Folder containing your subfolders.  
    output_csv_file = "image_annotations.csv"  
    create_annotation_csv(root_directory, output_csv_file)
Example output: 
filename,label
Ulcer/Ulcer_2024-08-07-08-28-10_81061.bmp,Ulcer
Ulcer/Ulcer_2024-08-07-08-29-37_82025.bmp,Ulcer
Ulcer/Ulcer_2024-08-07-08-29-07_43887.bmp,Ulcer
Ulcer/Ulcer_2024-08-07-08-28-10_43888.bmp,Ulcer
Ulcer/Ulcer_2024-08-07-08-30-31_30154.bmp,Ulcer
Ulcer/Ulcer_2024-08-07-08-27-27_96319.bmp,Ulcer