  Drinfeld suggested the definition of a certain endo-functor, called the
pseudo-identity functor, on the category of D-modules on an algebraic stack. We
extend this definition to an arbitrary DG category, and show that if certain
finiteness conditions are satisfied, this functor is the inverse of the Serre
functor. We apply this to the category of (g,K)-modules, and we stipulate that
the pseudo-identity functor is the analog of the Deligne-Lusztig functor. In
order to support this, we show that the pseudo-identity functor for
(g,K)-modules is isomorphic to the composition of cohomological and
contragredient dualities, which is parallel to the corresponding assertion for
p-adic groups in [BBK].
