Use default hash method to return hash value of a piece of string
        default setting use 'utf-8' encoding.

def of_text(self, text, encoding="utf-8"):
        """Use default hash method to return hash value of a piece of string
        default setting use 'utf-8' encoding.
        """
        m = self.hash_algo()
        m.update(text.encode(encoding))
        if self.return_int:
            return int(m.hexdigest(), 16)
        else:
            return m.hexdigest()