Function charToRole

charToRole(
    ch:
        | "b"
        | "q"
        | "n"
        | "r"
        | "p"
        | "k"
        | "B"
        | "Q"
        | "N"
        | "R"
        | "P"
        | "K",
): "pawn"
| "knight"
| "bishop"
| "rook"
| "queen"
| "king"

charToRole(
    ch: string,
): undefined | "pawn" | "knight" | "bishop" | "rook" | "queen" | "king"