Context. Daily step counts from users on two plans, Basic and Pro. Do Pro users actually move more? Overlay the two distributions to find out.
Your task. Write make_grouped_hist(df) that draws a seaborn histogram of steps with 4 bins, split by plan using hue, and returns the axes.
Example. hue="plan" colors each plan separately — and adds the legend for you.
Notes. No manual legend() call needed; seaborn builds it from the hue values.