Here's the code we wrote to make the lines;
dict(calc_diff(df))
df_diff.assign(limit=lambda d: d['diff_unit_tests'] < -1.771)['limit'].mean()
df_diff.assign(limit=lambda d: d['diff_asserts'] < -1.6857)['limit'].mean()
df_diff.assign(limit=lambda d: d['diff_user_stories'] < -1.1142)['limit'].mean()