import re


def is_valid_inchikey(inchikey: str) -> bool:
    """Return True if string has format of inchikey.

    Parameters
    ----------
    inchikey
        Input string to test if it format of an inchikey.
    """
    if inchikey is None:
        return False

    regexp = r"[A-Z]{14}-[A-Z]{10}-[A-Z]"
    if re.fullmatch(regexp, inchikey):
        return True
    return False