public override string ToString() {
StringBuilder sb = new StringBuilder("ColumnDef(");
sb.Append("Name: ");
sb.Append(Name);
sb.Append(",Validation_class: ");
sb.Append(Validation_class);
sb.Append(",Index_type: ");
sb.Append(Index_type);
sb.Append(",Index_name: ");
sb.Append(Index_name);
sb.Append(",Index_options: ");
sb.Append(Index_options);
sb.Append(")");
return sb.ToString();
}