Delete the instance from redis storage.

def delete(self):
        """
        Delete the instance from redis storage.
        """
        # Delete each field
        for field_name in self._fields:
            field = self.get_field(field_name)
            if not isinstance(field, PKField):
                # pk has no stored key
                field.delete()
        # Remove the pk from the model collection
        self.connection.srem(self.get_field('pk').collection_key, self._pk)
        # Deactivate the instance
        delattr(self, "_pk")