code: def set_epochrange(self, start_epoch, stop_epoch, step_size):
          
          self.start_epoch = start_epoch
          self.stop_epoch = stop_epoch
          self.step_size = step_size
  
          return None
docs: Set a range of epochs, all times are UT
  
          :param start_epoch: str;
             start epoch of the format 'YYYY-MM-DD [HH-MM-SS]'
          :param stop_epoch: str;
             final epoch of the format 'YYYY-MM-DD [HH-MM-SS]'
          :param step_size: str;
             epoch step size, e.g., '1d' for 1 day, '10m' for 10 minutes...
          :return: None
          :example: >>> import callhorizons
                    >>> ceres = callhorizons.query('Ceres')
                    >>> ceres.set_epochrange('2016-02-26', '2016-10-25', '1d')
  
          Note that dates are mandatory; if no time is given, midnight is assumed.