code: public int[] getIndexOfColumns(String... columnNames) {
          int[] out = new int[columnNames.length];
          for (int i = 0; i < out.length; i++) {
              out[i] = getIndexOfColumn(columnNames[i]);
          }
          return out;
      }
docs: Return the indices of the columns, given their namess
  
  @param columnNames Name of the columns to get indices for
  @return Column indexes