code: @Override
      public Schema transform(Schema schema) {
          int nCols = schema.numColumns();
          List<ColumnMetaData> meta = schema.getColumnMetaData();
          List<ColumnMetaData> newMeta = new ArrayList<>(nCols);
          newMeta.addAll(meta);
          newMeta.add(new StringMetaData(outputColumnName));
          return schema.newSchema(newMeta);
      }
docs: Get the output schema, given the input schema