code: def fit(self, volumes, energies):
          
          eos_fit = self.model(np.array(volumes), np.array(energies))
          eos_fit.fit()
          return eos_fit
docs: Fit energies as function of volumes.
  
          Args:
              volumes (list/np.array)
              energies (list/np.array)
  
          Returns:
              EOSBase: EOSBase object