def register_standard (id, source_types, target_types, requirements = []):
    """ Creates new instance of the 'generator' class and registers it.
        Returns the creates instance.
        Rationale: the instance is returned so that it's possible to first register
        a generator and then call 'run' method on that generator, bypassing all
        generator selection.
    """
    g = Generator (id, False, source_types, target_types, requirements)
    register (g)
    return g