Image_of_Element_is_Subset

import Mathlib.Data.Set.Basic
import Mathlib.Data.Set.Function

theorem Image_of_Element_is_Subset {α : Type _} {β : Type _} (f : α → β) (A : Set α) (s : α) (hs : s ∈ A) : {f s} ⊆ f '' A := by sorry