code: def _add_cat_dict(self,
                        cat_dict_class,
                        key_in_self,
                        check_for_dupes=True,
                        **kwargs):
          
          # Try to create a new instance of this subclass of `CatDict`
          new_entry = self._init_cat_dict(cat_dict_class, key_in_self, **kwargs)
          if new_entry is None:
              return False
  
          # Compare this new entry with all previous entries to make sure is new
          if cat_dict_class != Error:
              for item in self.get(key_in_self, []):
                  if new_entry.is_duplicate_of(item):
                      item.append_sources_from(new_entry)
                      # Return the entry in case we want to use any additional
                      # tags to augment the old entry
                      return new_entry
  
          self.setdefault(key_in_self, []).append(new_entry)
  
          return True
docs: Add a CatDict to this Entry if initialization succeeds and it
          doesn't already exist within the Entry.