def _create_reference_value_options(self, keys, finished_keys):
        """this method steps through the option definitions looking for
        alt paths.  On finding one, it creates the 'reference_value_from' links
        within the option definitions and populates it with copied options."""
        # a set of known reference_value_from_links
        set_of_reference_value_option_names = set()
        for key in keys:
            if key in finished_keys:
                continue
            an_option = self.option_definitions[key]
            if an_option.reference_value_from:

                fully_qualified_reference_name = '.'.join((
                    an_option.reference_value_from,
                    an_option.name
                ))
                if fully_qualified_reference_name in keys:
                    continue  # this referenced value has already been defined
                              # no need to repeat it - skip on to the next key
                reference_option = an_option.copy()
                reference_option.reference_value_from = None
                reference_option.name = fully_qualified_reference_name
                # wait, aren't we setting a fully qualified dotted name into
                # the name field?  Yes, 'add_option' below sees that
                # full pathname and does the right thing with it to ensure
                # that the reference_option is created within the
                # correct namespace
                set_of_reference_value_option_names.add(
                    fully_qualified_reference_name
                )
                self.option_definitions.add_option(reference_option)

        for a_reference_value_option_name in set_of_reference_value_option_names:
            for x in range(a_reference_value_option_name.count('.')):
                namespace_path = \
                    a_reference_value_option_name.rsplit('.', x + 1)[0]
                self.option_definitions[namespace_path].ref_value_namespace()

        return set_of_reference_value_option_names
this method steps through the option definitions looking for
        alt paths.  On finding one, it creates the 'reference_value_from' links
        within the option definitions and populates it with copied options.