old_contents: def check_happyNumbers(x):
  	aset = set()
  	while True:
  		s = sum(int(i)**2 for i in str(x))
  		if s in aset:
  			return False
  		elif s == 1:
  			return True
  		else:
  			aset = aset | {s}
  			x=s
  
  print check_happyNumbers(28)
new_contents: def check_happyNumbers(x):
  	aset = set()
  	while True:
  		s = sum(int(i)**2 for i in str(x))
  		if s in aset:
  			return False
  		elif s == 1:
  			return True
  		else:
  			# aset = aset | {s}
  			aset.add(s)
  			x=s
  
  print check_happyNumbers(20)
subject: set addition using add