Serialize datas to manifest structure with metas and references.

        Only references are returned, metas are assigned to attribute
        ``ManifestSerializer._metas``.

        Arguments:
            datas (dict): Data where to search for reference declarations. This
                is commonly the fully parsed manifest.

        Returns:
            collections.OrderedDict: Serialized enabled references datas.

def serialize(self, datas):
        """
        Serialize datas to manifest structure with metas and references.

        Only references are returned, metas are assigned to attribute
        ``ManifestSerializer._metas``.

        Arguments:
            datas (dict): Data where to search for reference declarations. This
                is commonly the fully parsed manifest.

        Returns:
            collections.OrderedDict: Serialized enabled references datas.
        """
        self._metas = OrderedDict({
            'references': self.get_meta_references(datas),
        })

        return self.get_enabled_references(datas, self._metas['references'])