def check():
    """
    Checks the validity of commandline arguments.

    Parameters
    ----------
        None

    Returns
    -------
        error : string
            Error message if error occurs otherwise blank string.
    """


    error = ""
    if (args.sf < 2):
        error = "Error: --sf/slomo factor has to be atleast 2"
    if (args.batch_size < 1):
        error = "Error: --batch_size has to be atleast 1"
    if (args.fps < 1):
        error = "Error: --fps has to be atleast 1"
    if ".mkv" not in args.output:
        error = "output needs to have mkv container"
    return error

    Checks the validity of commandline arguments.

    Parameters
    ----------
        None

    Returns
    -------
        error : string
            Error message if error occurs otherwise blank string.
    
video_to_slomo.py