@classmethod
def RegisterCredentials(cls, credentials):
    """Registers a path specification credentials.

    Args:
      credentials (Credentials): credentials.

    Raises:
      KeyError: if credentials object is already set for the corresponding
          type indicator.
    """
    if credentials.type_indicator in cls._credentials:
        raise KeyError(
            'Credentials object already set for type indicator: {0:s}.'.
            format(credentials.type_indicator))
    cls._credentials[credentials.type_indicator] = credentials
