First of all "crash" means there was an error message. That is useful information.
get_contact_collider() is not a function on the player, so that's not going to work.
get_contact_collider_shape(), as I linked you above, is a method of
Physics2DDirectBodyState, which you have access to in
_integrate_forces(). You shouldn't be trying to do physics-related stuff in
Alternatively, you likely could get what you want using the RigidBody2D's
body_shape_entered signal, which will tell you the colliding shape information. Either way will get you the colliding shape.