input: 
  def convert_bitwise(x):
      """ Convert a positive integer to negative or vice versa using bitwise NOT operator.
      >>> convert_bitwise(5)
      -5
      >>> convert_bitwise(-3)
      3
      >>> convert_bitwise(0)
      0
      """
      if x >= 0:
          return ~x + 1
      else:
          return ~(x-1)
  
output:     if x >= 0:
          return ~x + 1
      else:
          return ~(x-1)