presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/model/RowSchema.java/RowSchema/toString
class RowSchema:    @Override
    public String toString()
    {
        StringBuilder builder = new StringBuilder("{");
        for (AccumuloColumnHandle columnHandle : columns) {
            builder.append(columnHandle.getName())
                    .append(' ')
                    .append(columnHandle.getType())
                    .append(',');
        }

        if (builder.length() > 1) {
            builder.deleteCharAt(builder.length() - 1);
        }

        builder.append('}');
        return builder.toString();
    }