':param name_id: Identifier of the subject, a NameID instance
:param sources: Sources for information about the subject
:return:'

def stale_sources_for_person(self, name_id, sources=None):

    if (not sources):
        sources = self.cache.entities(name_id)
    sources = [m for m in sources if (not self.cache.active(name_id, m))]
    return sources
