docs: public List<ColumnMetaData> differences(Schema schema) {
          List<ColumnMetaData> ret = new ArrayList<>();
          for (int i = 0; i < schema.numColumns(); i++) {
              if (!columnMetaData.contains(schema.getMetaData(i)))
                  ret.add(schema.getMetaData(i));
          }
  
          return ret;
      }