t: Numeric vector. Thresholds of the generalized Pareto distributions
alpha_ini: Numeric vector. Initial Pareto alphas of the generalized Pareto distributions.
alpha_tail: Numeric vector. Tail Pareto alphas of the generalized Pareto distributions.
truncation: NULL or Numeric vector. If truncation is not NULL and truncation > t, then the generalized Pareto distributions are truncated at truncation (resampled generalized Pareto)
Returns
A vector of n samples from the (truncated) generalized Pareto distribution with parameters t, alpha_ini and alpha_tail