∀ (J : Type u_1) [inst : CategoryTheory.Category.{u_2, u_1} J] (j : J)
  (g : CategoryTheory.BiconeHom J CategoryTheory.Bicone.left (CategoryTheory.Bicone.diagram j)),
  g ≍ CategoryTheory.BiconeHom.left j → CategoryTheory.BiconeHom.left j = g