  // glmer stuff, see table 3 of
  // https://cran.r-project.org/web/packages/lme4/vignettes/lmer.pdf
  int<lower=0> t;               // num. terms (maybe 0) with a | in the glmer formula
  array[t] int<lower=1> p;      // num. variables on the LHS of each |
  array[t] int<lower=1> l;      // num. levels for the factor(s) on the RHS of each |
  int<lower=0> q;               // conceptually equals \sum_{i=1}^t p_i \times l_i
  int<lower=0> len_theta_L;     // length of the theta_L vector

  // hyperparameters for glmer stuff; if t > 0 priors are mandatory
  vector<lower=0>[t] shape; 
  vector<lower=0>[t] scale;
  int<lower=0> len_concentration;
  array[len_concentration] real<lower=0> concentration;
  int<lower=0> len_regularization;
  array[len_regularization] real<lower=0> regularization;
