{J : CategoryTheory.Limits.MulticospanShape} →
  {motive : CategoryTheory.Limits.WalkingMulticospan J → Sort u} →
    (t : CategoryTheory.Limits.WalkingMulticospan J) →
      t.ctorIdx = 0 → ((a : J.L) → motive (CategoryTheory.Limits.WalkingMulticospan.left a)) → motive t