Pion--kaon source size (upper panel) and emission asymmetry (lower panel) for Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV as a function of $\langle$d$N_{\rm ch}/$d$\eta\rangle^{1/3}$. The solid lines show predictions from calculation of source size and emission asymmetry using the THERMINATOR 2 model with default and selected values of additional delay with a mean time of $\Delta\uptau$ and width $\upsigma_{\text t}$ for kaons . The statistical and systematic uncertainties are combined and shown as square brackets. The uncertainty related to the fraction of primary pairs is reported separately as a correlated model-dependent systematic uncertainty of $\pm$15\% (20\%).