from typing import Dict
from typing import Optional


def get_case_insensitive_dict_key(d: Dict, k: str) -> Optional[str]:
    """
    Within the dictionary ``d``, find a key that matches (in case-insensitive
    fashion) the key ``k``, and return it (or ``None`` if there isn't one).
    """
    for key in d.keys():
        if k.lower() == key.lower():
            return key
    return None