human
I wrote the below code

    def configure_subclass_mapper(discriminator):
        try:
            sub_mapper = mapper.polymorphic_map[discriminator]
        except KeyError:
            raise AssertionError(('No    such    polymorphic_identity    %r    is    defined' % discriminator))
        if (sub_mapper is mapper):
            return None
        return instance_processor(sub_mapper, context, path, adapter, polymorphic_from=mapper)
    return configure_subclass_mapper

What's a good function header?
 Here's a good function header?
assistant
#Here's a good function header.

def _configure_subclass_mapper(mapper, context, path, adapter):