def DeregisterHelper(cls, resolver_helper):
    """Deregisters a path specification resolver helper.

    Args:
      resolver_helper (ResolverHelper): resolver helper.

    Raises:
      KeyError: if resolver helper object is not set for the corresponding
          type indicator.
    """
    if resolver_helper.type_indicator not in cls._resolver_helpers:
      raise KeyError(
          'Resolver helper object not set for type indicator: {0:s}.'.format(
              resolver_helper.type_indicator))

    del cls._resolver_helpers[resolver_helper.type_indicator]