What are the average ages for male and female students?
return students ;return #1 that  are male ;return #1 that  are female ;return ages of #2 ;return ages of #3 ;return the  average of #4 ;return the  average of #5 ;return #6 ,  #7
['select', 'filter', 'filter', 'project', 'project', 'aggregate', 'aggregate', 'union']