def check_inputs(ttl_files):
    """check_input.
    will return a list of ttl files, more advanced
    functionality can be added if needed (validation, etc)
    Parameters
    ==========
    ttl_files: string or list
        full paths to ttl files   
    Returns
    =======
        list of ttl files
    """
    if isinstance(ttl_files,str): ttl_files = [ttl_files]
    return ttl_files