code: @Override
      public List<BooleanColumn> getDummies() {
          List<BooleanColumn> results = new ArrayList<>();
  
          // createFromCsv the necessary columns
          for (Short2ObjectMap.Entry<String> entry : keyToValueMap().short2ObjectEntrySet()) {
              BooleanColumn column = BooleanColumn.create(entry.getValue());
              results.add(column);
          }
  
          // iterate over the values, updating the dummy variable columns as appropriate
          for (short next : values) {
              String category = getValueForKey(next);
              for (BooleanColumn column : results) {
                  if (category.equals(column.name())) {
                      //TODO(lwhite): update the correct row more efficiently, by using set rather than add & only
                      // updating true
                      column.append(true);
                  } else {
                      column.append(false);
                  }
              }
          }
          return results;
      }
docs: Returns a list of boolean columns suitable for use as dummy variables in, for example, regression analysis,
  select a column of categorical data must be encoded as a list of columns, such that each column represents
  a single category and indicates whether it is present (1) or not present (0)
  
  @return a list of {@link BooleanColumn}