Top row: $\pi^\pm$K$^0_{\rm S}$ correlation functions experimentally measured (blue dots) compared with PYTHIA8+GEANT3 simulations (red squares) obtained in pp collisions at $\sqrt{s}=13$ TeV for $0-100\%$ multiplicity class and $k_T>0$ (left), $0-100\%$ multiplicity class and $k_{\rm T}<0.5$ GeV/$c$ (center), and 0--5$\%$ multiplicity class and $k_{\rm T}<0.5$ GeV/$c$ (right). The PYTHIA8+GEANT3 correlation function is normalized tothe data at $k^*=0.5$ GeV/c. Bottom row: Ratio of Data to PYTHIA8+GEANT3 simulations for the three studied cases Statistical uncertainties are represented by bars.