gofCopula(copula, x, N = 1000,          method = c("Sn", "SnB", "SnC", "Rn"),          estim.method = c("mpl", "ml", "itau", "irho", "itau.mpl"),          simulation = c("pb", "mult"), verbose = interactive(), ties = NA,          ties.method = c("max", "average", "first", "last", "random", "min"),          fit.ties.meth = eval(formals(rank)$ties.method), ...)其中"Sn", "SnB", "SnC", "Rn"、  simulation = c("pb", "mult"), 到底指的什么方法？谁能用将统计原理帮我讲清楚