code: public List<String> top(int n) {
          List<String> top = new ArrayList<>();
          StringColumn copy = this.copy();
          copy.sortDescending();
          for (int i = 0; i < n; i++) {
              top.add(copy.get(i));
          }
          return top;
      }
docs: Returns the largest ("top") n values in the column
  
  @param n The maximum number of records to return. The actual number will be smaller if n is greater than the
  number of observations in the column
  @return A list, possibly empty, of the largest observations