code: public Table dropDuplicateRows() {
  
          Table sorted = this.sortOn(columnNames().toArray(new String[columns().size()]));
          Table temp = emptyCopy();
  
          for (int row = 0; row < rowCount(); row++) {
              if (temp.isEmpty() || !Rows.compareRows(row, sorted, temp)) {
                  Rows.appendRowToTable(row, sorted, temp);
              }
          }
          return temp;
      }
docs: Returns the unique records in this table
  Note: Uses a lot of memory for a sort