code: def make_query(self, query_type, expression, **kwargs):
          
          data = dict(expression=str(expression),
                      stop=kwargs.get('stop', datetime.utcnow()))
          data.update(kwargs)
  
          for k in ['start', 'stop']:
              if k in data:
                  try:
                      data[k] = data[k].isoformat()
                  except AttributeError:
                      pass
  
          r = requests.get(self.evaluator_url + query_type, params=data)
          r.raise_for_status()
  
          return r.json()
docs: Actually perform the query,
          try to convert datetime to isoformat on the fly