How can i resize a particle through scripts?

So you see I'm trying to make a fireball script. When i hold the attack ,it gets bigger. But that's not the problem,i want the particles to resize over time.

In the properties of the ParticleEmitter,you can use NumberSequence to make it so the particles get smaller over time. I tried to do that through scripting,but it seems like it doesn't work.

local Seq = NumberSequence.new(0,10)

help me ;-;