{motive : Mathlib.Tactic.Widget.StringDiagram.Node → Sort u} →
  (t : Mathlib.Tactic.Widget.StringDiagram.Node) →
    t.ctorIdx = 0 →
      ((a : Mathlib.Tactic.Widget.StringDiagram.AtomNode) → motive (Mathlib.Tactic.Widget.StringDiagram.Node.atom a)) →
        motive t