docs: def save(self, internal=False, meta=None, index_fields=None):
          """
          Save's object to DB.
  
          Do not override this method, use pre_save and post_save methods.
  
          Args:
              internal (bool): True if called within model.
                  Used to prevent unneccessary calls to pre_save and
                  post_save methods.
              meta (dict): JSON serializable meta data for logging of save operation.
                  {'lorem': 'ipsum', 'dolar': 5}
              index_fields (list): Tuple list for indexing keys in riak (with 'bin' or 'int').
                  bin is used for string fields, int is used for integer fields.
                  [('lorem','bin'),('dolar','int')]
  
          Returns:
               Saved model instance.
          """
          for f in self.on_save:
              f(self)
          if not (internal or self._pre_save_hook_called):
              self._pre_save_hook_called = True
              self.pre_save()
          if not self.deleted:
              self._handle_uniqueness()
          if not self.exist:
              self.pre_creation()
          old_data = self._data.copy()
          if self.just_created is None:
              self.setattrs(just_created=not self.exist)
          if self._just_created is None:
              self.setattrs(_just_created=self.just_created)
          self.objects.save_model(self, meta_data=meta, index_fields=index_fields)
          self._handle_changed_fields(old_data)
          self._process_relations(internal)
          if not (internal or self._post_save_hook_called):
              self._post_save_hook_called = True
              self.post_save()
              if self._just_created:
                  self.setattrs(just_created=self._just_created,
                                _just_created=False)
                  self.post_creation()
          self._pre_save_hook_called = False
          self._post_save_hook_called = False
          if not internal:
              self._initial_data = self.clean_value()
          return self