# File lib/travis/client/session.rb, line 94
      def find_one(entity, id = nil)
        raise Travis::Client::Error, "cannot fetch #{entity}" unless entity.respond_to?(:many) and entity.many
        return create_entity(entity, entity.id_field => id) if entity.id? id
        cached(entity, :by, id) { fetch_one(entity, id) }
      end