code: def H(self, phase, T):
          
  
          try:
              return self._phases[phase].H(T)
          except KeyError:
              raise Exception("The phase '{}' was not found in compound '{}'."
                              .format(phase, self.formula))
docs: Calculate the enthalpy of a phase of the compound at a specified
          temperature.
  
          :param phase: A phase of the compound, e.g. 'S', 'L', 'G'.
          :param T: [K] temperature
  
          :returns: [J/mol] Enthalpy.