I do not know How to call the OncollisionEnter 2D Function in other places of the code.In THIS CODE I WOULD LIKE TO CALL IT IN THE VOID UPDATE.

void OnCollisionEnter2D (Collider2D col)
    {
        if (col.gameObject.name == "Front_Buildings")
        {

            GetComponent<Animator>().SetBool("isGrounded", true);

        }
 }