I need some help for python AI. I can't understand some codes for python AI. I need to understand this code. So please help me.

code :

def str(self):
if self.nature is 'AI':
return self.name+' ('+self.nature+')'+' as '+self.colour
else:
return self.name+' as '+self.colour

In this code 'AI' is used. But I dont understand this AI. Actually this code is used for chess game. So I need to understand this code for my work. please help me.

'AI' clearly appears to be a string in the above code.
Probably, this code is to start a game. The string 'AI' is assigned when you select a particular character to the other party in the game(here the computer).
When the code checks for the string, it wants to find out who is playing using black or white