docs: def _get_bits(bits=None, target=None):
      """
      Determine the number of bits to pack/unpack.
      """
  
      if bits is not None:
          bits = int(bits)
          if bits in (8, 16, 32, 64):
              return bits
          else:
              raise ValueError('bits needs to be 8, 16, 32 or 64')
      else:
          return int((target if target is not None else pwnypack.target.target).bits)