code: public int size() {
  
          int acc = 0;
  
          for (Map.Entry<String, List<Cell>> entry : cells.entrySet()) {
              acc += entry.getValue().size();
          }
  
          return acc;
      }
docs: Returns the total number of cell(s) this object contains.
  
  @return the number os Cell objects contained in this Cells object.