PermGroupOps.PgGroup( G )
This function converts a permutation group G of prime power order p^d
into an ag group P such that the presentation corresponds to a p-step
central series of G. This central composition series is constructed by
calling CentralCompositionSeriesPPermGroup (see
CentralCompositionSeriesPPermGroup). An isomorphism from the ag group
to the permutation group is bound to P.bijection.
There is no dispatcher to this function, it must be called as
PermGroupOps.PgGroup.
GAP 3.4.4