Following the Contributing page, I am creating this issue with regard to contributing ported code that I have been working on that will make pvl_PVsyst_parameter_estimation, and all associated code to make it run, accessible to pvlib-python. The comprehensive list of functions that I have / will be porting is:

pvl_PVsyst_parameter_estimation
pvl_singlediode
est_single_diode_param
Schumaker_QSpline
calc_theta_phi_exact
update_io_known_n
update_rsh_fixed_pt
pvl_lambertw

I have already finished and done some testing with the scripts that are bolded while the others are either in the process of being completed or have not been started yet.