old_contents: class Solution:
  
      # @param A, a list of integer
  
      # @return an integer
  
      def singleNumber(self, A):
  
          return reduce(lambda x, y: x ^ y, A)
  
new_contents: class Solution:
      # @param A, a list of integer
      # @return an integer
      def singleNumber(self, A):
          return reduce(lambda x, y: x ^ y, A)
  
subject: Update answer.py