import ast


def convert_fc_shapes(arg):
    """
    Returns a tuple of sizes to use in FC layers.

    For examples, converts "100" -> (100,)
    "100,200" -> (100,200)
    """
    arg = arg.strip()
    if not arg:
        return ()
    arg = ast.literal_eval(arg)
    if isinstance(arg, int):
        return (arg,)
    if isinstance(arg, tuple):
        return arg
    return tuple(arg)