def get_scalar_mirrored_target_option(self, option_name, target):
    """Get the attribute `field_name` from `target` if set, else from this subsystem's options."""
    mirrored_option_declaration = self._mirrored_option_declarations[option_name]
    return mirrored_option_declaration.get_mirrored_scalar_option_value(target)
Get the attribute `field_name` from `target` if set, else from this subsystem's options.