code: def save_index(self, filename):
          ''' Save the current Layout's index to a .json file.
  
          Args:
              filename (str): Filename to write to.
  
          Note: At the moment, this won't serialize directory-specific config
          files. This means reconstructed indexes will only work properly in
          cases where there aren't multiple layout specs within a project.
          '''
          data = {}
          for f in self.files.values():
              entities = {v.entity.id: v.value for k, v in f.tags.items()}
              data[f.path] = {'domains': f.domains, 'entities': entities}
          with open(filename, 'w') as outfile:
              json.dump(data, outfilef save_index(self, filename):
          ''' Save the current Layout's index to a .json file.
  
          Args:
              filename (str): Filename to write to.
  
          Note: At the moment, this won't serialize directory-specific config
          files. This means reconstructed indexes will only work properly in
          cases where there aren't multiple layout specs within a project.
          '''
          data = {}
          for f in self.files.values():
              entities = {v.entity.id: v.value for k, v in f.tags.items()}
              data[f.path] = {'domains': f.domains, 'entities': entities}
          with open(filename, 'w') as outfile:
              json.dump(data, outfile)
docs: Save the current Layout's index to a .json file.
  
          Args:
              filename (str): Filename to write to.
  
          Note: At the moment, this won't serialize directory-specific config
          files. This means reconstructed indexes will only work properly in
          cases where there aren't multiple layout specs within a project.