example.gd

extents KinematicBody2D

var is_repelling: bool = false

[...]

func _process(delta):
    
    if not is_repelling:
        for i in get_slide_count():
            var collision = get_slide_collision(i)

            if (collision.collider.is_in_group("name")):
                repel(collision)

func repel(collision: KinematicCollision2D) -> void:
    var collision_body = collision.collider
    is_repelling = true

    # my knockback
    # collision_body.repel(self)