v3.2.0

Read-only accessors for the data a birth is drawn from, for code that builds on births (families, cohorts, charts):

• countries(): the countries with data.
• age_weights(country, sex): the age pyramid as relative weights, ages 0 to 100.
• life_expectancy(country, sex): the figure le_remaining is computed from.
• cohort_of(year) (static): the generational cohort label birth::cohort carries.

Generated output and the data hash are unchanged.