from typing import List
from typing import Any


def _prepare_args(args: List[Any]) -> List[str]:
    """Prepare args

    This does following conversions:

        [['a']] -> ['a']
        [1]     -> ['1']
        [None]  -> ['']

    """
    if not args:
        return args

    result = []
    for arg in args:
        if not isinstance(arg, list):
            arg = [arg]
        result += ['' if a is None else str(a) for a in arg]
    return result