code: def T_stock(self, V_stock):
          
          return Stock.T_stock(self, V_stock, self.Q_stock()).to(u.hr)
docs: Return the amount of time at which the stock of materal will be
          depleted.
  
          :param V_stock: Volume of the stock of material
          :type V_stock: float
  
          :return: Time at which the stock will be depleted
          :rtype: float