old_contents: """
  Write a function that takes an unsigned integer and
  returns the number of ’1' bits it has
  (also known as the Hamming weight).
  
  For example, the 32-bit integer ’11' has binary
  representation 00000000000000000000000000001011,
  so the function should return 3.
  """
  
  
  def count_ones(n):
      """
      :type n: int
      :rtype: int
      """
      counter = 0
      while n:
          counter += n & 1
          n >>= 1
      return counter
  
new_contents: """
  Write a function that takes an unsigned integer and
  returns the number of ’1' bits it has
  (also known as the Hamming weight).
  
  For example, the 32-bit integer ’11' has binary
  representation 00000000000000000000000000001011,
  so the function should return 3.
  """
  
  
  def count_ones(n):
      """
      :type n: int
      :rtype: int
      """
      if n < 0:
          return
      counter = 0
      while n:
          counter += n & 1
          n >>= 1
      return counter
  
subject: Check if the input is negative