def METHOD_NAME(files, filter):
    """
    Filter a list of files based on a filter
    Args: files (list): list of files to filter
    Args: filter (string): filter to apply to the list of files
    returns: list: list of filtered files
    """
    filtered_files = []
    for file in files:
        if filter.lower() in file.lower():
            filtered_files.append(file)
    return filtered_files