/**
 * Takes a hexadecimal string and, when the hexedecimal is valid,
 * returns it as a decimal string.
 */
export function hexToDec(hexStr: string): string | null;
/**
 * Takes a decimal string and, when the decimal is valid,
 * returns it as a hexadecimal string.
 */
export function decToHex(decStr: string, opts?: { prefix?: boolean | undefined }): string | null;