Nuisance asymmetries in the decay of $D_S^{\pm} \rightarrow K^{\pm}\pi^{\pm}\pi^{\mp}$

The variation of the production and trigger asymmetry over the Dalitz plot in the decay of $D_s^{\pm} \rightarrow K^{\pm}\pi^{\pm}\pi^{\mp}$ in the LHCb detector is determined. Data is used from run-2 proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The variation is found to be subdominant in comparison to the statistical uncertainty on the CP asymmetry for the full run 2 data set and can therefore be neglected.