def to_s(evaluate_formulas=true)
      return '' if poi_cell.nil?

      if poi_cell.cell_type == CELL_TYPE_FORMULA && evaluate_formulas == false
        formula_value
      else
        value.to_s
      end
    end
def to_s(evaluate_formulas=true)
      return '' if poi_cell.nil?

      if poi_cell.cell_type == CELL_TYPE_FORMULA && evaluate_formulas == false
        formula_value
      else
        value.to_s
      end
    end
Get the String representation of this Cell's value.

 If this Cell is a formula you can pass a false to this method and
 get the formula instead of the String representation.