dif_test                Score (LM) tests of differential step and item
                        functioning
dsf                     Likelihood ratio tests of differential step
                        functioning
dsf_design              Multigroup TPPCM design with group.equal and
                        group.partial
get_parts               Components of a fitted model
irt_pars                Item and group parameters in a compact table
item_test               Item-level score tests
m2                      Limited-information goodness of fit: M2,
                        RMSEA2, SRMSR, CFI, TLI
mi                      Modification indices for single step
                        discriminations
score_test              Score test against a less restricted TPPCM
sim_tppcm               Simulate item responses from a TPPCM
step_info               Step, item and test information
tppcm                   Step design for the TPPCM and its submodels
tppcmtree               TPPCM trees: model-based recursive partitioning
                        of step discriminations
wald_test               Wald test of equal step discriminations within
                        items
xxirt_tppcm             Fit TPPCM-family models with sirt::xxirt()
xxirt_vcov              Covariance matrix of an xxirt fit with shared
                        or fixed parameters
