code: def _calculate_T(self, H):
          
  
          # Create the initial guesses for temperature.
          x = list()
          x.append(self._T)
          x.append(self._T + 10.0)
  
          # Evaluate the enthalpy for the initial guesses.
          y = list()
          y.append(self._calculate_H(x[0]) - H)
          y.append(self._calculate_H(x[1]) - H)
  
          # Solve for temperature.
          for i in range(2, 50):
              x.append(x[i-1] - y[i-1]*((x[i-1] - x[i-2])/(y[i-1] - y[i-2])))
              y.append(self._calculate_H(x[i]) - H)
              if abs(y[i-1]) < 1.0e-5:
                  break
  
          return x[len(x) - 1]
docs: Calculate the temperature of the package given the specified
          enthalpy using a secant algorithm.
  
          :param H: Enthalpy. [kWh]
  
          :returns: Temperature. [°C]