∀ {X : Type u_1} [inst : TopologicalSpace X] (C : Set X) [inst_1 : Topology.CWComplex C] (n : ℕ)
  (i : Topology.CWComplex.cell C n),
  ∃ I,
    Set.MapsTo (↑(Topology.CWComplex.map n i)) (Metric.sphere 0 1)
      (∅ ∪ ⋃ m, ⋃ (_ : m < n), ⋃ j ∈ I m, ↑(Topology.CWComplex.map m j) '' Metric.closedBall 0 1)