IDEA: refactor pg_calendar() with dict?

[truth-quark]

For simplification extensibility, consider replacing this:

um2nc-standalone/umpost/um2netcdf.py

Lines 87 to 98 in 120dc47

	# Override the PP file calendar function to use Proleptic Gregorian rather than Gregorian.
	# This matters for control runs with model years < 1600.
	@property
	def pg_calendar(self):
	"""Return the calendar of the field."""
	# TODO #577 What calendar to return when ibtim.ic in [0, 3]
	calendar = cf_units.CALENDAR_PROLEPTIC_GREGORIAN
	if self.lbtim.ic == 2:
	calendar = cf_units.CALENDAR_360_DAY
	elif self.lbtim.ic == 4:
	calendar = cf_units.CALENDAR_365_DAY
	return calendar

with a dict:

 @property 
 def pg_calendar(self): 
    cal = {2: cf_units.CALENDAR_360_DAY,
           4: cf_units.CALENDAR_365_DAY}
    return cal.get(self.lbtim.ic, cf_units.CALENDAR_PROLEPTIC_GREGORIAN)