def _jar_id(jar):
    """Create a string identifier for the IvyModuleRef key.
    :param IvyModuleRef jar: key for a resolved jar
    :returns: String representing the key as a maven coordinate
    """
    if jar.rev:
      return '{0}:{1}:{2}'.format(jar.org, jar.name, jar.rev)
    else:
      return '{0}:{1}'.format(jar.org, jar.name)
Create a string identifier for the IvyModuleRef key.
    :param IvyModuleRef jar: key for a resolved jar
    :returns: String representing the key as a maven coordinate