code: def tofile(self, f):
          
          f.write(pack(self.FILE_FMT, self.error_rate, self.num_slices,
                       self.bits_per_slice, self.capacity, self.count))
          (f.write(self.bitarray.tobytes()) if is_string_io(f)
           else self.bitarray.tofile(f))
docs: Write the bloom filter to file object `f'. Underlying bits
          are written as machine values. This is much more space
          efficient than pickling the object.