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