code: def _check_unused_kwargs(self, kwargs):
          
          if len(kwargs.keys()) != 0:
              unused = ""
              for k in kwargs.keys():
                  unused += "'%s', "%k
              if unused[-2:] == ", ":     # get rid of trailing comma
                  unused = unused[:-2]
              raise Exception('Unused keys in kwargs: %s'%unused)
docs: Call this at the end of call module to check if all the kwargs have
          been used. Assumes kwargs were extracted using pop.