code: def SInt(value, width):
      
      return Operators.ITEBV(width, Bit(value, width - 1) == 1,
                             GetNBits(value, width) - 2**width,
                             GetNBits(value, width))
docs: Convert a bitstring `value` of `width` bits to a signed integer
      representation.
  
      :param value: The value to convert.
      :type value: int or long or BitVec
      :param int width: The width of the bitstring to consider
      :return: The converted value
      :rtype int or long or BitVec