private static MapTypeBuilder <TMapType> PassThroughNonNull(MapTypeBuilder <TMapType> builder)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            return(builder);
        }
 protected MapTypeBuilder(MapTypeBuilder <TMapType> builder)
     : this(PassThroughNonNull(builder).MapType)
 {
 }