code: def get_cartesian(self):
          
          coords = ['x', 'y', 'z']
          eq_sets = self._metadata['eq']['eq_sets']
          sym_ops = self._metadata['eq']['sym_ops']
          frame = pd.DataFrame(index=[i for v in eq_sets.values() for i in v],
                               columns=['atom', 'x', 'y', 'z'], dtype='f8')
          frame['atom'] = pd.Series(
              {i: self.loc[k, 'atom'] for k, v in eq_sets.items() for i in v})
          frame.loc[self.index, coords] = self.loc[:, coords]
          for i in eq_sets:
              for j in eq_sets[i]:
                  frame.loc[j, coords] = np.dot(sym_ops[i][j],
                                                frame.loc[i, coords])
          return Cartesian(frame)
docs: Return a :class:`~Cartesian` where all
          members of a symmetry equivalence class are inserted back in.
  
          Args:
              None
  
          Returns:
              Cartesian: A new cartesian instance.