The main purpose of print_std_errors
is to provide a convenient tool to match the standard
errors to certain parameter estimates. Note that if the model is intercept parametrized, there won't
be standard errors for the unconditional means, and vice versa. Also, there is no standard error for the
last mixing weight alpha_M because it is not parametrized.
Note that if linear constraints are imposed and they involve summations or multiplications, then the AR
parameter standard errors are printed separately as they don't correspond one-to-one to the model parameter
standard errors.