from typing import Any


def _make_arg_str(arg: Any) -> str:
    """Helper function to convert arg to str.

    :param arg: argument
    :type arg: Any
    :return: arg converted to str
    :rtype: str
    """
    arg = str(arg)
    too_big = len(arg) > 15 or "\n" in arg
    return "..." if too_big else arg