docs: def list_activities(self):
  
          ''' a method to retrieve the details for all activities currently supported
  
          :return: dictionary of response details with activities list inside json key
  
           {
              'headers': { ... },
              'code': 200,
              'error': '',
              'url': 'https://api.moves-app.com/api/1.1/activities'
              'json': [
                  {
                      "activity": "aerobics",
                      "geo": false,
                      "place": true,
                      "color": "bc4fff",
                      "units": "duration,calories"
                  },
                  ...
              ]
          }
          '''
  
          title = '%s.list_activities' % self.__class__.__name__
  
      # construct request parameters
          url_string = '%s/activities' % self.endpoint
  
      # send request
          response_details = self._get_request(url_string)
  
          return response_details