How do you get a Particle's process_material notifications

:information_source: Attention Topic was automatically imported from the old Question2Answer platform.
:bust_in_silhouette: Asked By ichster

I am am curious how to access the notifications that are sent to a Particles2D Process Material _notification() function. I know that the Particles2D’s script can control the parameters in the process_material with setters/getters (which defeats the need for accessing):

func _process():
    process_material.set_param(ParticlesMaterial.PARAM_INITIAL_LINEAR_VELOCITY, 50)
   celebrate_setting_the_linear_velocity()

But I am curious how to get the notifications.