colour.HKE_NAYATANI1997_METHODS# colour.HKE_NAYATANI1997_METHODS = CanonicalMapping({'VAC': ..., 'VCC': ...})# Define Nayatani (1997) Helmholtz-Kohlrausch effect (HKE) computation methods: variable achromatic colour (‘VAC’) and variable chromatic colour (‘VCC’). References [Nay97]
