def METHOD_NAME(self, p_force):
    # simple (but inefficient) collision response
    for a, entity_a in enumerate(self.entities):
        for b, entity_b in enumerate(self.entities):
            if b <= a:
                continue
            [f_a, f_b] = self.get_collision_force(entity_a, entity_b)
            if f_a is not None:
                if p_force[a] is None:
                    p_force[a] = 0.0
                p_force[a] = f_a + p_force[a]
            if f_b is not None:
                if p_force[b] is None:
                    p_force[b] = 0.0
                p_force[b] = f_b + p_force[b]
    return p_force