@Override
    public Optional<MemberShape> getMember(String memberName) {
        if ("key".equals(memberName)) {
            return Optional.of(key);
        }
        if ("value".equals(memberName)) {
            return Optional.of(value);
        }
        return Optional.empty();
    }
Get the key member shape of the map.

@return Returns the key member shape.
smithy-model/src/main/java/software/amazon/smithy/model/shapes/MapShape.java