Dear everyone,
     i have a question and i need your help. i want to refine loops (50-60 and 90-100) of my model after building model by modeller9.14. however, i don't know how to set the two regions. the part codes of my script is: 

return selection(self.residue_range('50:', '60:'),
               self.residue_range('90:', '100:'),
selection_status='INITIALIZE')

is right or not?  And what's the difference between  self.residue_range('90:', '100:') and  self.residue_range('90', '100')? thank you very much!
 ai yixin