def prop_modifier(self, cls: ClassDefinition, slot: SlotDefinition) -> str:
        """ Return the modifiers for the slot:
            (i) - inherited
            (m) - inherited through mixin
            (a) - injected
            (pk) - primary ckey

        @param cls:
        @param slot:
        @return:
        """
        pk = '(pk)' if slot.primary_key else ''
        inherited = slot.name not in cls.slots
        mixin = inherited and slot.name in \
                [mslot.name for mslot in [self.schema.classes[m] for m in cls.mixins]]
        injected = cls.name in self.synopsis.applytos and \
                   slot.name in [aslot.name for aslot in
                                 [self.schema.classes[a] for a in sorted(self.synopsis.applytos[cls.name].classrefs)]]
        return pk + '(a)' if injected else '(m)' if mixin else '(i)' if inherited else ''