∀ {α : Type u_1} {β : Type u_2} [inst : TopologicalSpace α] [inst_1 : AddCommGroup α] [inst_2 : LinearOrder α]
  [IsOrderedAddMonoid α] [OrderTopology α] {f : β → α} {x : Filter β} {a : α},
  Filter.Tendsto f x (nhds a) = ∀ ε > 0, ∀ᶠ (b : β) in x, |f b - a| < ε