def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        properties_to_expire = []
        if forward:
            properties_to_expire.extend(self.FORWARD_PROPERTIES)
        if reverse and not self.abstract:
            properties_to_expire.extend(self.REVERSE_PROPERTIES)

        for cache_key in properties_to_expire:
            try:
                delattr(self, cache_key)
            except AttributeError:
                pass

        self._get_fields_cache = {} 

def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        properties_to_expire = []
        if forward:
            properties_to_expire.extend(self.FORWARD_PROPERTIES)
        if reverse and not self.abstract:
            properties_to_expire.extend(self.REVERSE_PROPERTIES)

        for cache_key in properties_to_expire:
            try:
                delattr(self, cache_key)
            except AttributeError:
                pass

        self._get_fields_cache = {} 

def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        if forward:
            for cache_key in self.FORWARD_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        if reverse and not self.abstract:
            for cache_key in self.REVERSE_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        self._get_fields_cache = {} 

def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        if forward:
            for cache_key in self.FORWARD_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        if reverse and not self.abstract:
            for cache_key in self.REVERSE_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        self._get_fields_cache = {} 

def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        if forward:
            for cache_key in self.FORWARD_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        if reverse and not self.abstract:
            for cache_key in self.REVERSE_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        self._get_fields_cache = {} 

def _expire_cache(self, forward=True, reverse=True):
        # This method is usually called by apps.cache_clear(), when the
        # registry is finalized, or when a new field is added.
        if forward:
            for cache_key in self.FORWARD_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        if reverse and not self.abstract:
            for cache_key in self.REVERSE_PROPERTIES:
                if cache_key in self.__dict__:
                    delattr(self, cache_key)
        self._get_fields_cache = {}