docs: def is_equal(self, another, limit=0.8):
          """
          Determine two simhash are similar or not similar.
  
          :param another: another simhash.
          :param limit: a limit of the similarity.
          :return: if similarity greater than limit return true and else return false.
          """
          if another is None:
              raise Exception("Parameter another is null")
  
          if isinstance(another, int):
              distance = self.hamming_distance(another)
          elif isinstance(another, Simhash):
              assert self.hash_bit_number == another.hash_bit_number
              distance = self.hamming_distance(another.hash)
          else:
              raise Exception("Unsupported parameter type %s" % type(another))
  
          similarity = float(self.hash_bit_number - distance) / self.hash_bit_number
          if similarity > limit:
              return True
          return False