converts seconds to a string in terms of 
        seconds -> years to show complexity of algorithm

def show_time_as_short_string(self, seconds):
        """ 
        converts seconds to a string in terms of 
        seconds -> years to show complexity of algorithm
        """
        if seconds < 60:
            return str(seconds) + ' seconds'
        elif seconds < 3600:
            return str(round(seconds/60, 1)) + ' minutes'
        elif seconds < 3600*24:
            return str(round(seconds/(60*24), 1)) + ' hours'
        elif seconds < 3600*24*365:
            return str(round(seconds/(3600*24), 1)) + ' days'
        else:
            print('WARNING - this will take ' + str(seconds/(60*24*365)) + ' YEARS to run' )
            return str(round(seconds/(60*24*365), 1)) + ' years'