Lists bunch of directories efficiently.

    Args:
      urn: Urn to list children.
      limit: Max number of children to list.
      age: The age of the items to retrieve. Should be one of ALL_TIMES,
        NEWEST_TIME or a range.

    Returns:
      RDFURNs instances of each child.

def ListChildren(self, urn, limit=None, age=NEWEST_TIME):
    """Lists bunch of directories efficiently.

    Args:
      urn: Urn to list children.
      limit: Max number of children to list.
      age: The age of the items to retrieve. Should be one of ALL_TIMES,
        NEWEST_TIME or a range.

    Returns:
      RDFURNs instances of each child.
    """
    _, children_urns = list(
        self.MultiListChildren([urn], limit=limit, age=age))[0]
    return children_urns