How to compute impulse responses for Bayesian estimation SVAR from BSVARS package in R using code provided in GitHub?

Question

I am trying to generate impulse responses for structural var using the BSVARS package for the already given model in the package by the following code available in GitHub. but I am getting an error. how do I rectify this error?

library(bsvars)
data(us_fiscal_lsuw)
specification  = specify_bsvar_sv$new(us_fiscal_lsuw, p = 4)
set.seed(123)
burn_in        = estimate_bsvar_sv(10, specification)
posterior      = estimate_bsvar_sv(50, burn_in$get_last_draw())
# normalise the posterior
BB            = posterior$last_draw$starting_values$B     
B_hat         = diag(sign(diag(BB))) %*% BB                
bsvars::normalise_posterior(posterior, B_hat)              

compute_impulse_responses <- function(posterior, horizon) {
  
  stopifnot("Argument posterior must contain estimation output from the estimate function." = any(class(posterior)[1] == c("PosteriorBSVAR", "PosteriorBSVARMSH", "PosteriorBSVARMIX", "PosteriorBSVARSV")))
  stopifnot("The posterior output must be normalised for the impulse responses to be interpretable." = posterior$is_normalised())
  stopifnot("Argument horizon must be a positive integer number." = horizon > 0 & horizon %% 1 == 0)
  
  posterior_B     = posterior$posterior$B
  posterior_A     = posterior$posterior$A
  N               = dim(posterior_A)[1]
  p               = (dim(posterior_A)[2] - 1) / N
  S               = dim(posterior_A)[3]
  
  qqq             = .Call(`_bsvars_bsvars_ir`, posterior_B, posterior_A, horizon, p)
  
  irfs            = array(NA, c(N, N, horizon + 1, S))
  for (s in 1:S) irfs[,,,s] = qqq[s][[1]]
  class(irfs)     = "PosteriorIR"
  
  return(irfs)
}

irf           = compute_impulse_responses(posterior, horizon = 8)

Error in compute_impulse_responses(posterior, horizon = 8) : 
  object '_bsvars_bsvars_ir' not found

at first i had problem with first if not argument but i rectified it. but i am encountering this error, which i am not sure what to do?

Error in compute_impulse_responses(posterior, horizon = 8) : object '_bsvars_bsvars_ir' not found