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