code: def _get_facet_chempots(self, facet):
          
          complist = [self.qhull_entries[i].composition for i in facet]
          energylist = [self.qhull_entries[i].energy_per_atom for i in facet]
          m = [[c.get_atomic_fraction(e) for e in self.elements] for c in
               complist]
          chempots = np.linalg.solve(m, energylist)
          return dict(zip(self.elements, chempots))
docs: Calculates the chemical potentials for each element within a facet.
  
          Args:
              facet: Facet of the phase diagram.
  
          Returns:
              { element: chempot } for all elements in the phase diagram.