'Compute the symbolic KL divergence of two categorical distributions'

def kl_sym(self, old_dist_info_vars, new_dist_info_vars):

    old_prob_var = old_dist_info_vars['prob']
    new_prob_var = new_dist_info_vars['prob']
    return TT.sum((old_prob_var * (TT.log((old_prob_var + TINY)) - TT.log((new_prob_var + TINY)))), axis=2)
