def _days_in_month(year, month):
assert <NUM_LIT:1> <= month <= <NUM_LIT:12>, month<EOL>if month == <NUM_LIT:2> and _is_leap(year):<EOL><INDENT>return <NUM_LIT><EOL><DEDENT>return _DAYS_IN_MONTH[month]<EOL>
year, month -> number of days in that month in that year.