v1.5.5

• reduce memory footprint of ‘fitc’ and ‘full_scale_tapering’ GP approximations
• add ‘t’ and ‘t_fix_df’ likelihoods
• add ‘num_parallel_threads’ parameter so that users can control the number of parallel CPU threads
• [R-package] make 'gpb.grid.search.tune.parameters' and 'tune.pars.bayesian.optimization' more robust
• [python-package] make 'tune_pars_TPE_algorithm_optuna' more robust
• [R-package][python-package] fix bug in handling of 'line_search_step_length' parameter in hyper parameter tuning functions
• add option gp_approx = 'vecchia_latent'