def add_field(self, field):
        """Add the received field to the model."""
        self.remove_field(field.name)
        self._fields[field.name] = field

        if field.default is not None:
            if six.callable(field.default):
                self._default_callables[field.key] = field.default
            else:
                self._defaults[field.key] = field.default
Add the received field to the model.