Cant set shader parameter on custom visual shader

[TheBricktop]

After some tweaking ive stumbled into a problem :
ive made simple visual shader and gave it a TextureUniform called "Emission"
In godot python ive referenced the material with the shader and called

  self.material.set_shader_param( "Emission", self.texture )

but im getting an error :

also when i do

  print(self.material.get_shader())

it returns None, so im guessing either im making some cryptic mistake or there is a bug that does not allow the shader to be used.