def add_content_type(self, ct):
        """
        Add a CoRE Link Format ct attribute to the resource.

        :param ct: the CoRE Link Format ct attribute
        """
        lst = self._attributes.get("ct")
        if lst is None:
            lst = []
        if isinstance(ct, str):
            ct = defines.Content_types[ct]
        lst.append(ct)
        self._attributes["ct"] = lst
Add a CoRE Link Format ct attribute to the resource.

        :param ct: the CoRE Link Format ct attribute