RStan - Problem in stan_file model code - Variational Bayes - r

Question

I am trying to do Variational inference, so that I can get the best approximating distribution with respect to the target distribution: a Normal-Inverse-Wishart.
Normal-Inverse-Wishart distribution
However when I compile the stan file with the model code it gives the error:
Error in stanc(file = file, model_code = model_code, model_name = ?>model_name, : 0
Syntax error in 'string', line 16, column 14 to column 15, parsing >error:
Expected "generated quantities {" or end of file after end of model >block.
I have tried to investigate what this is referring to but I require some help. My R code is:
stan_file <- "RStan VI model.stan"
stan_model <- rstan::stan_model(file = stan_file) // Error occurs at this line
The RStan file model code is:
data {
int<lower=1> N; // number of assets
real<lower=0> nu0; // prior confidence for sigma
matrix[N, N] sigma_0; // prior sigma
real<lower=0> T0; // prior confidence for mu
vector[N] mu0; // prior mu
}
parameters {
matrix[N, N] sigma;
vector[N] mu;
}
transformed parameters {
matrix[N, N] a;
matrix[N, N] b;
a = sigma0*nu0;
b = sigma/T0;
}
model {
target += inv_wishart_lpdf(sigma | nu0, a);
target += normal_lpdf(mu | mu0, b);
}
I even tried changing the last section of the model code to:
model {
sigma ~ inv_wishart(nu0, a);
mu ~ normal(mu0, b);
}
But still same error. Would anyone know what the error is and how I can fix it?
Many thanks.
Best,
Nihaar