code: def age(self, **kwargs):
          
          if kwargs.get('days', None) is not None:
              self._age += kwargs.get('days')
              return
          if kwargs.get('hours', None) is not None:
              self._age += kwargs.get('hours') / 24.
              return
          if kwargs.get('minutes', None) is not None:
              self._age += kwargs.get('minutes') / 24. / 60.
              return
          if kwargs.get('seconds', None) is not None:
              self._age += kwargs.get('seconds') / 24. / 60. / 60.
              return
  
          raise KeyError("Could not age particle, please specify 'days', 'hours', 'minutes', or 'seconds' parameter")
docs: Age this particle.
  
          parameters (optional, only one allowed):
              days (default)
              hours
              minutes
              seconds