code: def add_unique_identity(db, uuid):
      
      with db.connect() as session:
          try:
              add_unique_identity_db(session, uuid)
          except ValueError as e:
              raise InvalidValueError(e)
docs: Add a unique identity to the registry.
  
      This function adds a unique identity to the registry.
      First, it checks if the unique identifier (uuid) used to create the
      identity is already on the registry. When it is not found, a new unique
      identity is created. Otherwise, it raises a 'AlreadyExistError' exception.
  
      :param db: database manager
      :param uuid: unique identifier for the identity
  
      :raises InvalidValueError: when uuid is None or an empty string
      :raises AlreadyExistsError: when the identifier already exists
          in the registry.