The author describes the exact solution of a \(4\)-dimensional quantum gravity with nonvanishing cosmological constant. It is expressed as the partition function of the Chern-Simons theory with nonvanishing source, depending on metric variables. For the Cauchy surface equivalent to a \(3\)-sphere a perturbative expansion and the form of the wavefunction are written. The author suggests that this perturbative Chern-Simons wavefunction can be relevant for the description of the inflationary period of “our Universe”.