Plots in docs no longer work as expected with last arviz versions

[danielandresarcones]

For the last Arviz versions, the inference data variables are sorted in alphabetical order. The plots in the documentation are generated by the order defined when setting the inverse problem, which is no longer preserved by arviz. The result is

pair_plot_array = create_pair_plot(
    inference_data,
    emcee_solver.problem,
    true_values=true_values,
    focus_on_posterior=True,
    show_legends=True,
    title="Sampling results from emcee-Solver (pair plot)"
)

The solution is to simply indicate the variable names in the desired order when creating the plot:

pair_plot_array = create_pair_plot(
    inference_data,
    emcee_solver.problem,
    true_values=true_values,
    focus_on_posterior=True,
    show_legends=True,
    title="Sampling results from emcee-Solver (pair plot)",
    var_names= ["$a$", "$b$", "$\\sigma$"]
)

The density of lines needs to be specified as well. The solution is simple, but all the documentation examples should be checked.