The strict transforms on cons #
The recursion of the strict transforms H_0 = H, H_{i+1} = closure of π_i⁻¹(H_i ∖ Z_i)
along a sequence (strictTransformSeq, the "birational transform H⁰_i of H⁰" of
[Kol07, Definition 78]) restarts, on the constructor form cons ψ hY rest, from the strict
transform of H by the first blow-down, with centre Y: an induction on the stage
(cons_strictTransformSeqAux_succ, rfl at every step because cons puts the head before the
fields of rest by Fin.cases over finStages), with Z_0 = cosupp I_Y = Y.
The strict transforms of H along cons ψ hY rest after the first step are those of rest
starting from the strict transform of H by the first blow-down, with centre cosupp I_Y.
The recursion of the strict transforms on the constructor form, indexed by Fin and with
Z_0 = Y.